I was reading the latest article up on Hardwood Paroxysm, regarding the infamous “long 2″ and it’s role in offensive and defensive efficiency, and was intrigued by the apparent disconnect between above- and below-average defensive teams and the percentage of long 2s they force opponents to take. As described in the article, the correlation between forcing long 2s and better defensive efficiency seems much stronger in below-average defensive teams than the elite defensive teams. Why is that? Why does forcing long 2s suddenly become less important when you start talking about the best defenses in the NBA?
I’d warrant that the key difference is this: the best defensive teams in the NBA don’t always need to force long 2s. The conventional wisdom (and, by extension, the statistical framework) doesn’t apply equally to good defensive teams. That sounds illogical, though. If long 2s are indeed the least valuable shots in the NBA, why would any team not pursue the advantage of forcing opponents into those shots?
Let’s not blind ourselves by looking exclusively at numbers. Consider those teams in the “elite” defensive efficiency range. Each has the benefit of a standout defensive player or players, an exceptional defensive system, or most likely a combination of both. San Antonio has Tim Duncan, Orlando has Dwight Howard, Boston has Garnett/Rondo, Cleveland had LeBron. Milwaukee has a great system plus perennial DPOY-snub Andrew Bogut. The Lakers have a great coach and a bunch of good defenders. Charlotte, Oklahoma City, and Miami all had solid defensive schemes and players in place.
The point is – and I don’t think it’s too much of a stretch – those teams all have factors contributing to their defense that are far more important than opponent shot distributions. In improperly-applied mathematical terms, the defensive efficiency of above-average teams is more a function of their own ability than their opponent’s shot selection. Meanwhile, those teams who can’t (or don’t) play high-caliber defense are far more subject to the performance of their opponents. Conceivably, the efficiency rankings for those below-average teams are a result of which teams randomly gave up more high- vs. low-percentage shots. Obviously this isn’t the exclusive factor – we can all agree that basketball is more complex than just shot selection, and we would expect the graph to be perfectly correlated in such a one-variable system. But the correlation is strong enough to suggest that affecting shot selection is a useful defensive technique. It is, however, still subject to an occasional hot-shooting night from the opponent.
In Basketball on Paper, Dean Oliver explains how inconsistency tends to drag teams toward a .500 record. The discrepancy in HP’s graph suggests that the best defensive teams avoid such inconsistency by excelling at factors that are easier to control. Maybe they have a good shot-blocker, or they defend pick-and-rolls well. If you imagine an idealized team that blocks a very high percentage of shots at the rim, it might even be advantageous to funnel opponents inside, rather than forcing long 2s. The point is, good defenses force opponents to conform to a game-plan that favors the defender. Teams who can’t do this tend to perform better when opponents shoot bad shots. Thus, the best teams can play effective defense independent of opponent shot selections.