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Re: Offensive Rebounding Part of Offensive Rating

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  • Dean Oliver
    ... I will say that it was the conceptually most difficult aspect of what I ve had to do. ... But this isn t actually true. A lot of offensive rebounders
    Message 1 of 11 , Apr 3, 2004
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      --- In APBR_analysis@yahoogroups.com, "dan_t_rosenbaum"
      <rosenbaum@u...> wrote:
      > I very much agree that offensive rebounds should be part of an
      > offensive rating, but I think it is very tough to come up with the
      > right way to do it.

      I will say that it was the conceptually most difficult aspect of what
      I've had to do.

      >
      > The problem with the offensive rebounding part is that unlike the
      > points part or assist part, there is no negative associated with
      > offensive rebounds. Players trying to score are at risk of missed
      > shots and turnovers, implying that increasing the number of points
      > possessions will not necessarily increase a player's offensive
      > rating. Players attempting to get assists do so at the risk of
      > turnovers, so trying to get more assists will not necessarily
      > increase a player's offensive rating.
      >
      > But a player attempting to get more offensive rebounds takes no risk
      > (in his offensive rating), except for maybe an occasional turnover.
      > Thus, players who specialize in offensive rebounds are almost
      > guaranteed to have high offensive ratings.

      But this isn't actually true. A lot of offensive rebounders don't
      have high offensive ratings, in fact. And the ones that do have very
      low possession usage. In other words, it reflects the fact that they
      aren't taking a lot of risks. The tradeoff between possession usage
      and efficiency is still maintained. My skill curves do show that
      these guys, like Ben Wallace and Dennis Rodman, with high efficiency
      mainly through offensive boards would drop off significantly if they
      tried to do more.

      You might have said that later...

      >
      > My approach, without going into gory detail for now, is to split up
      > possessions into three parts - points, assists, and offensive
      > rebounds. Turnovers are apportioned to the points and assists part
      > according to their respective proportions of total possessions.
      > Then I calculate separate "offensive ratings" for each category
      > separately with offensive rebounds being measured as a percentage of
      > total team offensive rebounding opportunities (adjusting for minutes
      > played).
      >
      > This gives me three separate offensive ratings with three very
      > different scales. I normalize all three scales to have the same
      > mean and standard deviation as the minutes-weighted distribution for
      > points per effective field goal attempt. Then I add them together
      > weighting them by their respective proportion of total possessions.
      >
      > This methodology does tend to reward specialists, but overall I do
      > not think it gives any particular advantage to assist producers
      > versus points producers or offensive rebound producers versus assist
      > producers.
      >
      > Hopefully, this is enough of a description for people to get an idea
      > of what I am doing.

      Not sure I get it, but it will have to wait for a month until I come back.

      DeanO

      Dean Oliver
      Author, Basketball on Paper
      http://www.basketballonpaper.com
      "Oliver goes beyond stats to dissect what it takes to win. His breezy
      style makes for enjoyable reading, but there are plenty of points of
      wisdom as well. This book can be appreciated by fans, players,
      coaches and executives, but more importantly it can be used as a text
      book for all these groups. You are sure to learn something you didn't
      know about basketball here." Pete Palmer, co-author, Hidden Game of
      Baseball and Hidden Game of Football
    • bchaikin@aol.com
      The problem with the offensive rebounding part is that unlike the points part or assist part, there is no negative associated with offensive rebounds..... But
      Message 2 of 11 , Apr 3, 2004
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        The problem with the offensive rebounding part is that unlike the points part or assist part, there is no negative associated with offensive rebounds.....

        But a player attempting to get more offensive rebounds takes no risk (in his offensive rating), except for maybe an occasional turnover. Thus, players who specialize in offensive rebounds are almost guaranteed to have high offensive ratings....

        the act of actually getting an offensive or defensive rebound has no negative to it because both are in fact completely positive acts - there is no negative to getting a rebound, just as there is no negative to getting a steal. a missed shot is a free ball, like a jump ball, that everyone on the floor theoretically has access to. what you are failing to take into consideration, by implying that there is no negative to a rebound, is that whenever a shot is taken and missed, all 10 players on the court have an opportunity to get that rebound (theoretically an equal opportunity, in reality not, but nonetheless everyone does have the opportunity)....

        thus you can just as easily give no credit to the player that got an off (or def) rebound, but then credit a negative "missed rebound" to each of the other 9 players that missed getting that rebound each and every time someone does get one. the risk associated in getting an off or def rebound is in not getting it. the statement that "...a player attempting to get more offensive rebounds takes no risk...", if taken at face value, implies a misunderstanding of the process involved. when a player gets an off reb that's one off reb the his 4 other teammates did not get, and thus their "offensive ratings" suffer in the fact that they could have gotten that rebound but didn't, and the ratings of the 5 defensive players suffer in that each of them did not get an additional def rebound...

        shots, missed shots, turnovers, assists, are all acts that are credited to a player because he already has the ball in his hands. he has to at some point do something with it - shoot it, pass it, get fouled, or turn it over (dribbing leads to one of these), and we currently only measure three of these four parameters. but the only way for a player to gain possession of the ball in the first place - is on a throw in, a jump ball, receive a pass, or get a rebound. nobody keeps track of successful throw ins because the vast majority of the time its successful - when its not players gets TOs or STs. same with receiving a pass or gaining possession of a jump ball....

        thus each time a player takes a shot, we can just as easily forget crediting missed shots and rebounds, and call a missed shot followed by a def reb a "turnover" to the player who shot the ball, or call it "nothing" if the shot is missed and is followed by an off reb. but we don't do this - we break the measurement of the process down even further, into missed shots and rebounds. but since a missed shot is a free ball, like a jump ball, anyone getting the rebound is gaining possession of the ball for his team, and preventing the opposition from gaining possession, both of which have equal and opposite inherent value, and thus off and def rebounds are of the value as a team possession, a positive value...

        A lot of offensive rebounders don't have high offensive ratings, in fact.  And the ones that do have very low possession usage.  In other words, it reflects the fact that they aren't taking a lot of risks.

        this is in fact the reality...

        My skill curves do show that these guys, like Ben Wallace and Dennis Rodman, with high efficiency mainly through offensive boards would drop off significantly if they tried to do more.

        if trying to do more means other than getting more off rebounds in general i would tend to agree because the vast majority of very good off rebounders have low touches/min and high %TOs, meaning high rates of turnovers per ball possession, and consequently these are not the people you want having the ball in their hands on offense. this year for example danny fortson, reggie evans, chris mihm, nazr mohammed, jahidi white, all excellent off rebounders, turn the ball over more than 10% of the time they get it. but then their are players like shaq who are very good off rebounders and only turn the ball over on 6% of their ball possessions, and thus you do want them to have the ball because he is such an efficient scorer...

        bob chaikin
        bchaikin@...



      • roland_beech
        ... actually I think there is a way to measure a negative associated with offensive rebounding to mitigate the effect somewhat. Namely defensive rebounds
        Message 3 of 11 , Apr 3, 2004
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          > The problem with the offensive rebounding part is that unlike the
          > points part or assist part, there is no negative associated with
          > offensive rebounds.

          actually I think there is a way to measure a negative associated
          with offensive rebounding to mitigate the effect somewhat.
          Namely "defensive rebounds allowed"

          if we measure the ratio of a player's offensive rebounds to the
          times the other team or the other team's counterpart player gets the
          defensive rebound you have some basis for forming an adjustment for
          the player based on the expectations for the position the player
          plays at.

          So a center who grabs 3 rebounds, but gives up 12 defensive rebounds
          to the opposing center would be underperforming relative to a guard
          who grabs 2 off rebounds to 3 def rebs allowed...

          at the same time with usage rates as Dean/Bob mention you can also
          adjust to downgrade the Rodman types.

          Another avenue is to look at "first shot offense" versus "second+
          shot offense" within possessions. I'll be getting round to an
          article on this at some point (no doubt after the regular season
          concludes) and it will be interesting to see with a guy like Dampier
          what his numbers are for the first shot (he will be very strong on
          the second shot since many of his offensive rebounds lead to
          immediate dunks)

          of course, compartementalizing different areas on offense may also
          yield very notable numbers
        • Gabe Farkas
          your point about turnovers interests me. i m curious, using your method, what the flip side of turnovers is? in other words, if Ron Artest steals the ball from
          Message 4 of 11 , Apr 4, 2004
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            your point about turnovers interests me. i'm curious,
            using your method, what the flip side of turnovers is?

            in other words, if Ron Artest steals the ball from
            Shaq, then Artest is credited with a Steal (gaining of
            possession) and Shaq is "credited" with a Turnover
            (losing of possession). However, at the end of the
            game, the Lakers will almost invariably have
            registered more Turnovers than the Pacers have Steals.

            thus, is there any positive value credited to the
            Pacers in some way for the balance of Turnovers
            committed by the Lakers that were not the result of
            Steals?

            does that make sense?


            --- bchaikin@... wrote:
            > The problem with the offensive rebounding part is
            > that unlike the points part
            > or assist part, there is no negative associated with
            > offensive rebounds.....
            >
            >
            > But a player attempting to get more offensive
            > rebounds takes no risk (in his
            > offensive rating), except for maybe an occasional
            > turnover. Thus, players who
            > specialize in offensive rebounds are almost
            > guaranteed to have high offensive
            > ratings....
            >
            > the act of actually getting an offensive or
            > defensive rebound has no negative
            > to it because both are in fact completely positive
            > acts - there is no
            > negative to getting a rebound, just as there is no
            > negative to getting a steal. a
            > missed shot is a free ball, like a jump ball, that
            > everyone on the floor
            > theoretically has access to. what you are failing to
            > take into consideration, by
            > implying that there is no negative to a rebound, is
            > that whenever a shot is taken
            > and missed, all 10 players on the court have an
            > opportunity to get that
            > rebound (theoretically an equal opportunity, in
            > reality not, but nonetheless
            > everyone does have the opportunity)....
            >
            > thus you can just as easily give no credit to the
            > player that got an off (or
            > def) rebound, but then credit a negative "missed
            > rebound" to each of the other
            > 9 players that missed getting that rebound each and
            > every time someone does
            > get one. the risk associated in getting an off or
            > def rebound is in not getting
            > it. the statement that "...a player attempting to
            > get more offensive rebounds
            > takes no risk...", if taken at face value, implies a
            > misunderstanding of the
            > process involved. when a player gets an off reb
            > that's one off reb the his 4
            > other teammates did not get, and thus their
            > "offensive ratings" suffer in the
            > fact that they could have gotten that rebound but
            > didn't, and the ratings of
            > the 5 defensive players suffer in that each of them
            > did not get an additional
            > def rebound...
            >
            > shots, missed shots, turnovers, assists, are all
            > acts that are credited to a
            > player because he already has the ball in his hands.
            > he has to at some point
            > do something with it - shoot it, pass it, get
            > fouled, or turn it over (dribbing
            > leads to one of these), and we currently only
            > measure three of these four
            > parameters. but the only way for a player to gain
            > possession of the ball in the
            > first place - is on a throw in, a jump ball, receive
            > a pass, or get a rebound.
            > nobody keeps track of successful throw ins because
            > the vast majority of the
            > time its successful - when its not players gets TOs
            > or STs. same with receiving
            > a pass or gaining possession of a jump ball....
            >
            > thus each time a player takes a shot, we can just as
            > easily forget crediting
            > missed shots and rebounds, and call a missed shot
            > followed by a def reb a
            > "turnover" to the player who shot the ball, or call
            > it "nothing" if the shot is
            > missed and is followed by an off reb. but we don't
            > do this - we break the
            > measurement of the process down even further, into
            > missed shots and rebounds. but
            > since a missed shot is a free ball, like a jump
            > ball, anyone getting the rebound
            > is gaining possession of the ball for his team, and
            > preventing the opposition
            > from gaining possession, both of which have equal
            > and opposite inherent
            > value, and thus off and def rebounds are of the
            > value as a team possession, a
            > positive value...
            >
            > A lot of offensive rebounders don't have high
            > offensive ratings, in fact.�
            > And the ones that do have very low possession
            > usage.� In other words, it
            > reflects the fact that they aren't taking a lot of
            > risks.
            >
            > this is in fact the reality...
            >
            > My skill curves do show that these guys, like Ben
            > Wallace and Dennis Rodman,
            > with high efficiency mainly through offensive boards
            > would drop off
            > significantly if they tried to do more.
            >
            > if trying to do more means other than getting more
            > off rebounds in general i
            > would tend to agree because the vast majority of
            > very good off rebounders have
            > low touches/min and high %TOs, meaning high rates of
            > turnovers per ball
            > possession, and consequently these are not the
            > people you want having the ball in
            > their hands on offense. this year for example danny
            > fortson, reggie evans,
            > chris mihm, nazr mohammed, jahidi white, all
            > excellent off rebounders, turn the
            > ball over more than 10% of the time they get it. but
            > then their are players like
            > shaq who are very good off rebounders and only turn
            > the ball over on 6% of
            > their ball possessions, and thus you do want them to
            > have the ball because he is
            > such an efficient scorer...
            >
            > bob chaikin
            > bchaikin@...
            >
            >
            >
            >


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          • Mike G
            ... Good question, Gabe. The team gets indirect credit for turnovers forced in the final score. It amounts to an extra possession, and points off
            Message 5 of 11 , Apr 4, 2004
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              --- In APBR_analysis@yahoogroups.com, Gabe Farkas <gabefark@y...>
              wrote:
              > ... is there any positive value credited to the
              > Pacers in some way for the balance of Turnovers
              > committed by the Lakers that were not the result of
              > Steals?

              Good question, Gabe.

              The team gets indirect credit for "turnovers forced" in the final
              score. It amounts to an extra possession, and "points off
              turnovers" is a often-tracked quantity.

              Individual players don't get direct credit, as turnovers aren't
              credited to players on the defensive side. However, a number of
              accounting systems give indirect credit for team scoring
              differentials; as such, credit can be apportioned for a player's
              minutes on the floor.

              DanR's "corrections" of Roland's in/out figures would seem to
              incorporate this "uncounted" stat, within the team +/- .
            • Gabe Farkas
              Mike, I m not sure that s exactly where I was going with this. Basically, there are two kinds of turnovers: forced and unforced. Right? So, how can a forced
              Message 6 of 11 , Apr 5, 2004
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                Mike,

                I'm not sure that's exactly where I was going with
                this.

                Basically, there are two kinds of turnovers: forced
                and unforced. Right?

                So, how can a forced turnover occur? The other team
                steals the ball.

                And how can an unforced turnover occur? Throwing the
                ball away, double-dribble, traveling, charging, etc.

                My question is this: Other than steals, are there any
                recorded and tabulated statistics that are the
                flip-side of turnovers, or that lead to forced
                turnovers?

                Am I oversimplifying?

                --Gabe


                --- Mike G <msg_53@...> wrote:
                > --- In APBR_analysis@yahoogroups.com, Gabe Farkas
                > <gabefark@y...>
                > wrote:
                > > ... is there any positive value credited to the
                > > Pacers in some way for the balance of Turnovers
                > > committed by the Lakers that were not the result
                > of
                > > Steals?
                >
                > Good question, Gabe.
                >
                > The team gets indirect credit for "turnovers forced"
                > in the final
                > score. It amounts to an extra possession, and
                > "points off
                > turnovers" is a often-tracked quantity.
                >
                > Individual players don't get direct credit, as
                > turnovers aren't
                > credited to players on the defensive side. However,
                > a number of
                > accounting systems give indirect credit for team
                > scoring
                > differentials; as such, credit can be apportioned
                > for a player's
                > minutes on the floor.
                >
                > DanR's "corrections" of Roland's in/out figures
                > would seem to
                > incorporate this "uncounted" stat, within the team
                > +/- .
                >
                >


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              • Kevin Pelton
                ... On an individual level? Not yet. Have you seen DeanO s system? some explanation: http://f2.grp.yahoofs.com/v1/kJBxQCBiN7JnB9ZlKgeKp7wq-
                Message 7 of 11 , Apr 5, 2004
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                  > My question is this: Other than steals, are there any
                  > recorded and tabulated statistics that are the
                  > flip-side of turnovers, or that lead to forced
                  > turnovers?

                  On an individual level? Not yet. Have you seen DeanO's system?

                  some explanation:
                  http://f2.grp.yahoofs.com/v1/kJBxQCBiN7JnB9ZlKgeKp7wq-
                  7TntGsnvp2l3c49Cz03ntrXD0lEWDOD9UVsUoRMb4FPY-1Zb-
                  PwL31OG7yaucWm7L7I6WyNqF0YkQ/defstophandchart.xls

                  of course, it's all explained in more detail in Chapter 17 of The
                  Book:
                  http://www.basketballonpaper.com/book.html

                  One of the interesting things about DeanO's system is that while the
                  stats are primarily defensive, they can be used to evaluate offenses
                  as well. When you break out "unforced" turnovers that are really
                  charges and deflections off a player and out of bounds, etc., you get
                  really unforced turnovers -- throwing the ball out of bounds, for
                  example. It's a useful thing to know about an offense.
                • Michael Tamada
                  DeanO s defensive box scores that he (and his corps of volunteers) did for the WNBA did this: assign credit for turnovers to one or more defenders. Even
                  Message 8 of 11 , Apr 5, 2004
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                    DeanO's defensive box scores that he (and his
                    corps of volunteers) did for the WNBA did this:
                    assign credit for turnovers to one or more
                    defenders. Even steals, which under standard
                    statistics get credited to only one player, might
                    get credited to two if, e.g. in the opinion of the
                    stats-keeper, one player stood up the dribbler with
                    a double-team, enabling the other to grab the ball.

                    If it was something like a 5-second violation or
                    shot clock violation, that credit went to the whole
                    team ... or did it go to the 5 people on the floor?
                    I forget, but the latter would make sense.

                    However, those are special statistics not normally
                    collected. For most situations, I think MikeG's
                    answer is correct; these unforced turnovers only
                    show up very indirectly in the defenders' stats.


                    --MKT

                    -----Original Message-----
                    From: Gabe Farkas [mailto:gabefark@...]
                    Sent: Monday, April 05, 2004 7:55 AM


                    Mike,

                    I'm not sure that's exactly where I was going with
                    this.

                    Basically, there are two kinds of turnovers: forced
                    and unforced. Right?

                    So, how can a forced turnover occur? The other team
                    steals the ball.

                    And how can an unforced turnover occur? Throwing the
                    ball away, double-dribble, traveling, charging, etc.

                    My question is this: Other than steals, are there any
                    recorded and tabulated statistics that are the
                    flip-side of turnovers, or that lead to forced
                    turnovers?

                    Am I oversimplifying?

                    --Gabe


                    --- Mike G <msg_53@...> wrote:
                    > --- In APBR_analysis@yahoogroups.com, Gabe Farkas
                    > <gabefark@y...>
                    > wrote:
                    > > ... is there any positive value credited to the
                    > > Pacers in some way for the balance of Turnovers
                    > > committed by the Lakers that were not the result
                    > of
                    > > Steals?
                    >
                    > Good question, Gabe.
                    >
                    > The team gets indirect credit for "turnovers forced"
                    > in the final
                    > score. It amounts to an extra possession, and
                    > "points off
                    > turnovers" is a often-tracked quantity.
                    >
                    > Individual players don't get direct credit, as
                    > turnovers aren't
                    > credited to players on the defensive side. However,
                    > a number of
                    > accounting systems give indirect credit for team
                    > scoring
                    > differentials; as such, credit can be apportioned
                    > for a player's
                    > minutes on the floor.
                    >
                    > DanR's "corrections" of Roland's in/out figures
                    > would seem to
                    > incorporate this "uncounted" stat, within the team
                    > +/- .
                    >
                    >


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                  • Gabe Farkas
                    No, I haven t gotten a chance to read the book yet, but I ve been craving it for a few months now. Just haven t gotten around to picking it up. Can you
                    Message 9 of 11 , Apr 5, 2004
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                      No, I haven't gotten a chance to read the book yet,
                      but I've been craving it for a few months now. Just
                      haven't gotten around to picking it up. Can you
                      summarize the book in 25 words or less? Kidding, of
                      course.

                      what about taking Charges? are those tracked?

                      --- Kevin Pelton <kpelton08@...> wrote:
                      > > My question is this: Other than steals, are there
                      > any
                      > > recorded and tabulated statistics that are the
                      > > flip-side of turnovers, or that lead to forced
                      > > turnovers?
                      >
                      > On an individual level? Not yet. Have you seen
                      > DeanO's system?
                      >
                      > some explanation:
                      >
                      http://f2.grp.yahoofs.com/v1/kJBxQCBiN7JnB9ZlKgeKp7wq-
                      > 7TntGsnvp2l3c49Cz03ntrXD0lEWDOD9UVsUoRMb4FPY-1Zb-
                      > PwL31OG7yaucWm7L7I6WyNqF0YkQ/defstophandchart.xls
                      >
                      > of course, it's all explained in more detail in
                      > Chapter 17 of The
                      > Book:
                      > http://www.basketballonpaper.com/book.html
                      >
                      > One of the interesting things about DeanO's system
                      > is that while the
                      > stats are primarily defensive, they can be used to
                      > evaluate offenses
                      > as well. When you break out "unforced" turnovers
                      > that are really
                      > charges and deflections off a player and out of
                      > bounds, etc., you get
                      > really unforced turnovers -- throwing the ball out
                      > of bounds, for
                      > example. It's a useful thing to know about an
                      > offense.
                      >
                      >


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                    • Kevin Pelton
                      ... I m not sure whether you mean in DeanO s system or in general, so I ll answer both questions. In DeanO s system, they re counted as any other forced
                      Message 10 of 11 , Apr 5, 2004
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                        > No, I haven't gotten a chance to read the book yet,
                        > but I've been craving it for a few months now. Just
                        > haven't gotten around to picking it up. Can you
                        > summarize the book in 25 words or less? Kidding, of
                        > course.
                        >
                        > what about taking Charges? are those tracked?

                        I'm not sure whether you mean in DeanO's system or in general, so
                        I'll answer both questions.

                        In DeanO's system, they're counted as any other forced turnover, not
                        broken out (though certainly one *could* do that).

                        In real life, I think some teams track this (Denver?
                        http://www.nba.com/nuggets/news/notes.pdf ) but it's not official.
                        I'll take a look and see if they're in Harvey Pollack's book.

                        (As an aside, one of the neat things about being part of The Media is
                        the chance to see what things teams track in their game notes, like
                        the Wolves with what we now know as "Roland Ratio" last year -- when
                        there was a lot of general scoffing at the notion that a team could
                        be 25 points better with its star player on the court.)
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