Uh oh, fellow basketball math nerds: we might have overcorrected.
The analytics movement has given us so many new ways to see and understand NBA basketball. I myself am an ardent subscriber, and I think we’re just starting to scratch the surface of what advanced metrics can teach us about the game.
But, like any form of analysis, the danger is in arriving at conclusions too fast for our own good. There are a couple of maxims born from the analytics movement that might be oversimplifications. We’ll publish one today and one tomorrow on Salt City Hoops.
Rebounding & transition defense
We’re increasingly hearing about teams who forego the offensive glass in an effort to get back and defend against transition.1 Obviously, you can’t battle for rebounds and stop the fast break… right?
There are a few ways to analyze this claim, but two seem the most simple: one is to see if offensive rebounding really moves the needle that much on offensive efficiency, and the other is to see if teams who rebound well at that end struggle to contain the counterattack.
The league’s two most efficient offenses are Miami and Portland2, who find themselves at opposite ends of the offensive rebound rate spectrum. Portland is the top offensive team largely because they erase 31.2%3 of their missed shots for a second chance. Miami has the second best offense in spite of the fact that they are dead last in ORR – primarily due to their ridiculous True Shooting number of 59.8%.
These polar examples made it clear I needed to find a way to measure how much ORR impacts a team’s offensive rating. I calculated the difference between their Offensive Efficiency rank and what their rank would be if it were based purely on TS%. Above-average ORR teams got 2.3 spots better in overall OE, a difference that’s pretty much negligible.4 But if you look at the elite ORR teams, their offenses get a lot more potent than they otherwise would. The top five ORR teams averaged 6.4 spots higher.
And how much transition defense are they sacrificing to cash in on that offensive improvement? Not much, actually.
The top eight ORR teams have an average ranking of 15th in defensive transition PPP. The eight teams who most often ignore the offensive glass for the sake of “getting back” off have an average ranking of 18th. Yep, the teams who fight for offensive rebounds, on average, defend transition BETTER than the teams who make a conscious decision to hurry back. Wow.
There are individual teams on both ends of the spectrum to support the popular view that ORR and transition D are mutually exclusive. You have the Clippers, who are 22nd in ORR and sport the league’s best transition defense5. Then there’s New Orleans, fourth in ORR and second worst in transition D6. But on the whole, a good offensive rebounding team is no more likely to struggle at stopping the break.
So why have we gotten this wrong? My guess is that the linear thinking of “if I’m battling for a rebound I’m not getting back” is far too tempting. What it ignores, though, is the truth that if I’m battling on the glass, the other team has to keep its guys there to battle with me. They’re taking special care not to allow me easy second buckets, so fewer of their guys are available to start the break. If the possession is still up for grabs, neither team is off to the races just yet.
That’s one hasty conclusion of the stat geeks that probably needs some more thinking. The next comes tomorrow.