Thursday, December 9, 2010

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.

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What you see above in the “Irving plays” section are Kyrie Irving’s minutes, along with number of points that Duke has scored and given up when he’s been on the floor.  The “Irving sits” obviously shows the same data for when he’s on the bench, and the last column shows the difference in net points per 40 minutes between Duke’s performance with Irving in the game and rving out of the game.  Positive is good.  Take a look at the totals at the bottom: no matter how you slice it (remove blowouts, remove cupcakes, exclude the last game that he missed entirely), the Blue Devils have a higher Net/40 margin when Irving is out of the game.

Now, I originally did this because I thought it might show that Irving hurts them on defense, but we actually see that teams score at a higher rate when he sits.  However, I believe that’s largely due to a higher pace.  Looking at the offensive numbers, the difference between 84 and 96 pts/40  is almost surely not entirely due to increased efficiency; there must be some tempo increase there.  And if the tempo is faster, it’s pretty hard to say whether any of the increase in opponent scoring is due to worse defense.  Either way, it’s outweighed by the increase in Duke’s scoring, and the Devils end up with a better scoring margin when Irving sits.

That doesn’t necessarily mean that the Blue Devils are better when he’s on the bench, though.  It could also be that he happens to be sitting when the opponent’s best players are sitting, and the drop off from Irving to the Duke bench is less steep than the drop off from the starters to the bench of the opponent.  In fact, there’s anecdotal evidence that this is true: Irving’s bench minutes coincided with Curtis Kelly’s in the game versus Kansas Sate; and he left the game just as Shelvin Mack cramped up in the Butler game.  But the mere fact that Irving isn’t needed in order to take advantage of these missing players is a good sign for the Devils going forward.

On top of this, there’s even a reason why we might expect Duke to do better on offense without Irving.  Andre Dawkins is the most efficient player on offense for the Blue Devils, and as we learned via Luke Winn’s pretty pictures, Nolan Smith seems to be much better than Irving at getting the ball to Dawkins.

The bottom line is that, while losing a player like Kyrie Irving is unlikely to be a positive for any team, this Duke team seems to be put together in a way that may allow them to overcome this obstacle.  This isn’t a Purdue-losing-Hummel situation.  It’s more like a Kansas-without-Shelby situation, and that seems to be working out just fine for the Jayhawks.

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