Behind the Numbers: Rebound, Rebound, ReboundPosted by KCarpenter on December 29th, 2010
Kellen Carpenter is an RTC contributor.
One of my favorite features about watching basketball on television is when the cameras try to take you inside the locker room at halftime or inside the huddle during timeouts. This inside peek theoretically should be endlessly fascinating and unceasingly cool. I initially hoped to watch the coach draw up the next play, talk about strategic weaknesses he’d noticed, and generally be smart and insightful about the game. Of course, anyone who has ever seen a single one of these “inside peeks” knows that my hopes are routinely dashed. Inevitably, because the networks won’t actually broadcast any of the juicy strategic content of the huddles or halftime speeches, we instead get clip after clip of hoarse coaches exhorting their players to rebound, rebound, rebound, while the players gulp down water and nod with intense understanding. This is, of course, hilarious. Certainly the coach doesn’t think, “My players don’t know they are supposed to rebound,” while the players think “Rebounding! Of course! I was just going to stand around and ignore the ball, but your way is so much better!” It’s just an absurd little bit of theater since everyone knows how important rebounding is. Of course the players are trying to get the rebounds. Why wouldn’t they?
Rebounding has a cost. We tend to think of rebounding in terms of what it can grant a team: on the offensive end, a rebound offers another chance to score while it deprives the opponent of the same chance on the defensive end. Rebounding isn’t free, however. When a team attempts to rebound the ball, there is a trade-off. Every player who goes for an offensive rebound isn’t getting back on defense as quickly as he can, potentially giving up fast break points to the opposing team. Conversely, every player who attempts to get a defensive rebound isn’t leaking out, trying to get those high-percentage fast-break points. The potential cost of rebounding is forsaking fast-break points for your own team while giving up those same points to your opponent.
But does that matter? Offensive rebounding is important. When the shots aren’t falling and your opponents’ shots are, getting extra possessions is how you win games, and coming up with offensive rebounds is easier than getting steals or forcing other turnovers. In college basketball, the teams that win the championship are almost universally excellent at offensive rebounding. Does it have to be that way?
Not necessarily. In the NBA, the San Antonio Spurs dominated the early part of the last decade, winning four championships between 1999-2007, even while largely forsaking offensive rebounds. Gregg Popovich made the unusual though clever decision to avoid crashing the offensive boards and instead emphasized getting back on defense, preventing the opponent from scoring any fast break points. While San Antonio often trailed the league in offensive rebounds, in those years the average field goal percentage of Spur opponents sunk to ridiculous lows. Likewise, until fairly recently, San Antonio didn’t emphasize fast breaking, choosing instead to focus on securing the defensive rebound and limiting their opponents’ second chance opportunities. Instead of emphasizing their own offensive efficiency, the Spurs chose to gleefully flummox their opponents’ offensive plans. Those four NBA championships speak to the strategy’s success.
Or it at least speaks to the strategy’s success in the NBA. How does the strategy hold up in college? Does it even work? Are teams that elect to get back on defense instead of going for the rebound more effective at lowering their opponents effective field goal percentage? Well, let’s see. One easy way to check this would be to split Division I in half and compare the above median offensive rebounding teams with those below in terms of opponents’ effective field goal percentage. This quick and dirty check shows that teams that offensively rebound well hold opponents to 47.6% and teams that do so less allow 50.1%, a very slight difference that points to a trend in, well, the opposite direction. Whoops.
Of course, this first check was lousy: as I mentioned earlier, teams that get a lot of offensive rebounds are usually really good teams. Likewise, a portion of the teams that are included in the other half could very well simply be just bad at rebounding. What we are actually interested in is discrepancy: teams who are much better at defensive rebounding than offensive rebounding. So, instead, let’s compare opponents shooting based on the difference of their offensive and defensive rebounding rankings amongst Division I schools (as always, courtesy of the great Ken Pomeroy). Teams that were more than fifty spots higher on the defensive rebounding chart than the offensive rebounding chart held opponents to 48.8%, while teams that were significantly worse at defensive rebounding than offensive rebounding held opponents to… 48.8%. Teams that rebounded about the same on either end, however, shot… 48.9%. Well, damn.
So it looks like a wash. While the Spurs’ tactic may have been effective for Pop and the gang, it seems like no one in the college ranks has been able to translate an abstention on the offense boards into defensive gold. The upside? It seems like there isn’t much penalty for zealous offensive rebounding, at least as far as rough, overall percentages are concerned. Crash the boards with impunity! Offensive rebounding may have a cost, but right now, that cost seems pretty cheap, especially relative to the reward.