In Defense of Rebounding

This is a response to Steve Van Horn’s excellent arcticle in which he lays out the inadequacy of some box scores in determining wins. Defensive rebounds are a team activity and cannot reliably be credited in any percentage to the rebounder. The article can be read here.

The full back and forth conversation can be read here. (Wwert is me.)

I agree. Rebounds are the result to the successful completion of a good defense. Where I disagree is the area of rebounding as an individual skill.  Rebounds are consistent through time. If a good rebounder is switched to the bench, that bench’s lineup is going to get more rebounds. If he switches teams, that team will have more rebounds. Anything consistent through time is generally attributed to the individual skill of the rebounder. While the consecutive actions of teammates setting screens, the resulting defensive posture, the hedging, the skip pass, the iso distraction, the back screens are not recorded and  go uncredited, the fact that rebounds are consistently factored to a player(even when he leaves a team) makes me consider that rebounds to be a individual skill that is not as affected by other teammates as one might think.

according to wagesofwins.com

  • Rebounds are one of the most consistent statistics in team sports.  Players who rebounded well in the past tend to do in this in the future.  Players who are not good at rebounding in the past tend to be poor at this aspect of the game in the future.
  • Rebounds also vary across teams.  And teams that rebound well tend to employ better rebounders (or at least, avoid employing really bad rebounders).
  • Diminishing returns does exist.  This is seen with respect to Wins Produced in general and also with respect to defensive rebounds (but not, apparently, with respect to offensive rebounds).  The effect, though, is small. This is seen when we estimate the size of the diminishing returns effect.  It is also seen when we re-estimate player productivity with different value for defensive rebounds.
  • Although rebounds do have a substantial impact on wins, it is shooting efficiency – not rebounding – that is the most important determinant of a player’s Wins Produced.

(Sidenote completely unscientific: I play pick-up like most hobby sport statisticians. My shot is pretty bad. But I’ve always been a good rebounder. To me, rebounding is a skill. The percentages of the left side rolling to the right. The 50/50 ball. The particular English on the ball as it travels through the your enemies’ fingers. Over-thinking things is probably one of the reasons my shot is so bad/slow.)

From the stats, Wins Produced explains 90+% of the wins. Win Score per Minute has a 95% correlation with Wins Produced. So yeah, the question of that formula being overly sympathetic to rebounds is moot to me since it basically works 95% of the time. If you treat players like gambling bets, and if a formula comes along that has those odds, you don’t worry about that formula.

The new formula accredits only 50% of defensive rebounds to  the Win Score. It does not affect most of the positions too much. The PFs and Centers move down 3 spots maybe. In general, that .50% accreditation affects a very minuscule portion of the rankings. To sum it up, my rankings are 90% correlated with Wins Produced which is explains wins 95% of the time. Even if Wins Produced had 75% Explanatory Power, the gambler in me would take it. Wouldn’t you?

50% is erring in the side of caution. If we made it 25%, i have no doubt that the Win Score to WP correlation would suffer but it would still be quite a tool since the WP48 formula is so successful.

While I see the thesis that defensive rebounds are a team activity, I think situations where team rebounds are a team activity are far fewer. I think that players, actively thinking, and predicting and guiding the ball generate rebounding opportunities for themselves. It is hard to coordinate 4 man box out so that your tallguy can grab the DREB. It is much easier to be at the spot where the ball bounces to faster than your enemy.

This is just a matter of practicality for me.

If 25% credit to defensive rebounds gives me a greater correlation to Wins Produced, then i’m perfectly willing to do that. As such, I’m happy to use the 50% credit if only for the fact that some of the college kids do try to feed their seniors more rebounds and stats because they know the NBA Combines are coming up.

Yes, i am sidestepping the notion of whether or not rebounds can be used to gauge a player’s contributions to wins by totally relying on the efficacy of Wins Produced.

In conclusion, I don’t care if it’s a red panda or white cat, if it catches mice, then it’s a good cat.

(Cultural joke: Panda and Red Cat in Chinese are homonyms.)

I just want to predict future NBA stars. Maybe, in the future, we have AI who can analyze each game to give a variable defensive rebound coefficient per play but it is in my opinion that there are more situations where a rebounder is actively using his own skills to overpower his enemy and grabbing that sweet rebound, be it offensive or defensive. Whether or not their are more opportunities available to the rebounder because the team employs great man on man defense to call misses, should not be that statistically significant in the course of a season.

Additional very dry reading material which I did not want to messy this post with:

http://wagesofwins.com/2006/11/09/do-we-overvalue-rebounds/

http://sportsillustrated.cnn.com/vault/article/magazine/MAG1179946/2/index.htm

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To Read Part 2 of “In Defense of Rebounding” Click Here

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