Over The Back? What Over The Back? [Or: Minute-Adjusted Tempo-Free Rebounding Leaders]

[EDIT: I made a mistake in the original description of how to calculate OffReb+. I originally wrote that I multiplied by 70.2, but that’s incorrect. 70.2 is the average total rebounds in a game, for both teams, so I actually multiplied by half that (35.1) when I did the calculations. I just had a senior moment when I wrote it out.  Sorry about the confusion. The reason I noticed in the first place is that Mike Rogers over at The Only Colors has a couple nice posts up that expand on this idea (here and here).  Highly worth checking out.  I noticed his numbers didn’t jive with mine, and that’s how I spotted the error in the text.  So, thanks Mike!]

In case you missed it, Tennessee’s Brian Williams made what ESPN calls a “falling over-the-back buzzer beater” last night against Georgia. Bulldog Chris Barnes did a good job of boxing out, but Williams simply reached over his shoulder and snatched ball. The play reinforced a thought that’s been rolling around in my head: that instead of merely praising players with high offensive rebounding rates (whether measured by raw numbers or by offensive rebounding percentage [OR%]), we ought to be praising those that can do it without fouling. It’s not that the fouls themselves are so detrimental – if a player dials back the physicality enough to prevent the foul, he likely prevents the offensive rebound as well. But racking up fouls on high-risk offensive boards leads to reduced minutes for a player that provides at least some value in the form of rebounds.

Take a look at the current top ten offensive rebounders, by OR%, along with their fouls committed per 40 minutes (FC/40). Over half of these guys would foul out if asked to play play 40 minutes:

Hey, look – Brian Williams!

I thought it would be interesting to look at top ten that takes minutes played into account. This should penalize the foulers, plus it should knock out any small sample size wonders.

Gone, Gaddy, Gone

[EDIT: Ken Pomeroy posted a treatise on plus-minus which pointed out there’s a great deal of error inherent in the use of +/- data, something which has also been pointed out to me by John Ezekowitz.  At this point, I’d advise you to take everything I wrote below with a huge grain of salt.  And I doubt you’ll be seeing any more +/- analysis from me.]

About a month ago, I predicted that Duke would be fine without Kyrie Irving.  My reasoning was that, in the games while Irving was still healthy, Duke had actually performed better with Irving on the bench than they had while he was on the floor – about 7 net points per 40 minutes better.  Well, since the toe became The Toe, Duke has actually played ever so slightly better, with a post-Irving-injury adjusted efficiency margin of 39, compared to 37 with Irving:

Obviously that difference is insignificant, but the main point is that, so far, they’ve been fine.

I fear Washington’s prognosis for life without Abdul Gaddy is not so optimistic.  The same +/- data that soothed Blue Devil worries paints an uglier picture for the Huskies (click to enlarge):

Whereas Duke was 7 points per 40 minutes better with Irving on the bench, Washington has been almost 7 points per 40 minutes better with Gaddy in the lineup.  Some of the Twitter buzz hoped that the injury would give freshman CJ Wilcox a spot in the limelight.  That’d be great, as he has a team-high 131.8 ORtg in his limited time.  Taking a quick look at his +/- data, though, Washington has struggled with him in the game, despite his good offensive rating.  A safe bet here would be that Wilcox’s defense is a step down from Gaddy’s, though the KenPom individual stats don’t paint a big defensive difference between the two, other than Wilcox’s more frequent fouling. Whatever the reason for the struggles, somebody will have to step up if Washington hopes to retain its lofty rating.  If I’m Seth Davis, I’m changing my Washington grade from BUY to HOLD.

[On a side note, it’ll be a shame if this injury does end up impacting Washington, as I expect it to.  The Huskies were looking like a great ratings litmus test, as they were in the top 5 in both Pomeroy and Sagarin’s PREDICTOR, yet #23 and unranked in the two major polls.  Now watch, instead of tearing through the Pac-10 like their namesake through the Delaware, they’ll decline due to the impact of this injury, and the “you either win or lose” crowd will get a chance to trumpet their demise as a black mark against predictive ratings.]

How much will Kyrie Irving’s Absence affect Duke?

[EDIT: Ken Pomeroy posted a treatise on plus-minus which pointed out there’s a great deal of error inherent in the use of +/- data, something which has also been pointed out to me by John Ezekowitz.  At this point, I’d advise you to take everything I wrote below with a huge grain of salt.  And I doubt you’ll be seeing any more +/- analysis from me.]

There was a great post by the basketball distribution a few days ago about the effect of individual players on a team’s offense.  It ended up being extremely topical, given A) his choice of Duke as one of the example teams, and B) Kyrie Irving’s toe.  He calculated that removing Irving’s production from the Duke team would in theory reduce their offensive efficiency by about 3.1 points per 100 possessions, if the vacated minutes were filled proportionally by the other Duke players according to their share of minutes played so far, and if they all played at the same level.  (Obviously, those assumptions are questionable, but it’s the best that can be done with the available data.)

I thought I’d take a look at it from a different angle, one that is probably on even more tenuous footing, but that is nonetheless interesting.  I thought that perhaps, as a freshman, Irving might not be as advanced as his teammates defensively, so losing him might actually improve Duke’s defense.  The only way I could think of to investigate this was to use StatSheet’s plus-minus data to find out what has actually happened this year when Irving sits on the bench.  Before I get to the numbers, I should strongly emphasize that this data is very dependent on who all the other players in the game are, and we shouldn’t take it to seriously.  But I thought the results were drastic enough, and surprising enough, that they’d be of interest.