--- In APBR_analysis@y..., msg_53@h... wrote:
> --- In APBR_analysis@y..., "Dean Oliver" <deano@t...> wrote:
> Does Doug Steele's (or your) defensive index make the assumption
> that a player generally guards his counterpart at the same
Doug's method looks at matchups, yes. Mine doesn't. The methods
have different strengths and weaknesses. That's why I look at them
A key thing I've observed (and recorded) is that there is a lot of
help in defense. Big men are involved in defense a lot more. Every
drive to the middle brings a big man to help whereas not every post
move brings a perimeter guy to help. Big men then generally are keys
to defense, both positively and negatively. This also means that,
yes, players don't guard the same person all the time -- both because
they go in and out at different times and because of switching/help.
There is also the problem of fast breaks, where no one is guarding
> Has anyone got an approximation of the pct. of time a player
> actually is guarding the same position on the other team? Not sure
> if such an index would help anything, but it might lead to this
> number having a estimable degree of credibility.
I have a few game scores where I've tracked how often different
players were involved in stopping the opponent and in allowing a
> I am still looking for wide availability of individual +/- (is
> that the accepted term?) ratings. I have no doubt than we can
> effectively measure offense, optimistically; and that we can factor
> out the total team +/- to reach an individual's worth; and finally,
> that we can factor the player's offense out of his total worth, and
> that what remains could be called his defensive value.
This may be a way to start getting at defense. On its own, I am one
of those people who doesn't see too much value in the +/- #. But
perhaps it can be used to get at defense. There is still strong
correlation problems (always playing with the same people) and the
fact that it often reflects substitution pattern.
The +/- number is often in Harvey Pollack's stat guide, which Bob
Chaikin has for several years.
Journal of Basketball Studies