The Celtics’ demolition of the Lakers reminds me that the sport announcers would do well to put more emphasis on “rebound rates.” Like putt probabilities, the rebound rate basically tells you the probability that a team will get the next rebound.
Can you answer a fairly simple question: In the NBA if a team misses a shot, what is the probability that it will get the (offensive) rebound?
Most people I’ve asked think the probability is 10 percent or less. But it’s closer to 30 percent.
Game six was extraordinary not just because the Lakers had only two offensive rebounds, but because they shot so poorly (42.2) — so there were plenty of misses to rebound — and had only two offensive rebounds. As the great John Hollinger summed up:
[F]or the game [Los Angeles] had only two compared to 34 defensive boards for Boston. That’s a 6 percent rebound rate if you’re scoring at home; normally the offensive team gets around 30 percent.
One question that occurs to me is whether Lakers’ low number of offensive rebounds was just a matter of bad luck. If you have a 34 draws and if each draw has a 30 percent chance of success, then just by chance you might only have 2 successes. But a little analysis (using the same methodology that I used here to analyze political polls) suggests that we can reject the bad-luck hypotheses. The observed rebound rate of 6 percent is more than 3 standard deviations away from 30 percent — so there is less than a 1 percent chance that it would have occurred by chance.
Of course, just as the putting probability turns on the place on the green, the expected rebound probability turns on where the shot is taken and other factors. The website 82games.com gives a strategy for making the rebound probability turn on additional factors.
But even simple rebound rates can let us see things about the game for the first time.
1. This season Philadelphia had the highest probability of rebounding one of its own misses (31.8 percent), while Miami had a league last probability of 22.1 percent. Almost a 10 percent difference in getting the ball back when you miss can have a huge impact on games.
2. Rebound rates give you a better sense of who are the best individual rebounders. During the playoffs, Tim Duncan had the most defensive rebounds per game:
But Marcus Camby had a much higher probability of grabbing a defensive rebound. Camby himself grabbed more than a third of the other team’s misses:
3. Finally, rebound rates show that the art of the offensive rebound is distinctly different than the art of the defensive rebound.
Camby and Duncan, for example, rank only 35th and 21st among players in the playoffs in terms of offensive rebound probabilities. Who has a high offensive rebound rate? Dwight Howard had the best playoff probability (16.9 percent), but the Celtics’ Leon Powe is close behind grabbing 15.2 percent of the Celtics’ misses. Of course, readers of this blog shouldn’t be surprised at Powe’s success.
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You can say the deviation from the norm on offensive rebounds isn’t about bad luck, and I’d agree with you. However, it does NOT follow that there should be more rebound opportunities just because there are more missed shots.
If they’re forcing up shots, with people out of position or not running an offense or sharing the ball, the normal break downs or mismatches that lead to a weakside player being open aren’t going to be there. And if a team is getting creamed, players probably will not be crashing the boards in the same way for hustle plays.
In those circumstances, an outcome below the norm is predictable.
Two words: Dennis Rodman. Offensive rebounds and free throws are the low-hanging-fruit of both NBA and NCAA basketball. I’m always surprised more teams don’t make a bigger effort for the free stuff.
The probability that the Lakers were unlucky might be really small, but when you play as many games as these guys do, all sorts of improbable events can happen.
On the matter of whether the low offensive rebounds were luck or not.
Before the game you could have been pretty confident that a particular stat you were going to track would not stray to 3 standard deviations without a predicted cause. Looking backward is where the logical traps are. The sample space increases by orders of magnitude and could possibly extend as far as all the nba games ever played.
If it’s not clear, I vote luck.
Rebounding probability aside, announcers need work in many areas. It is absolutely maddening to hear would-be professionals constantly asking viewers to put themselves in the shoes of the team, coach, or a particular player. For example, Mark Jackson and Jeff van Gundy were incessantly telling us, “If you’re the Los Angeles Lakers…,” or “If you’re Doc Rivers….” I don’t know when, where, or with whom this began, but it has penetrated the commentary of just about every sport now.
I am not the Los Angeles Lakers or even Doc Rivers; just be a professional and say, “The Lakers would could make up some ground by focusing on offensive rebounding.”
Please?
Finally, rebound rates show that the art of the offensive rebound is distinctly different than the art of the defensive rebound.
From somebody who stopped watching the NBA years ago but plays pick-up now and again, yeah. Defensive rebounding is all about boxing out, which should be straightforward if your defensive positioning is sound (you’ll be closer to the basket). Offensive rebounding involves more effort and creativity in fighting through or around the box out for good rebound position.
Of course, a lot of pick-up players won’t bother to box out and also expect opponents to expend most of their effort on scoring instead of rebounding, making offensive boards a lot easier, and thus a pretty good way to build reputation with new teammates.
A lot of NBA teams make getting offensive rebounds a very low priority, since sending more players to get offensive rebounds leaves less players to defend the fast break.
Rebounding in general is a mixture of technique, teamwork, effort and luck. There are games when the ball just keeps falling into the other teams hands. But once the Lakers fell behind in game 6, they probably started showing significantly less effort in their rebounding. That and the Celtics had a significantly bigger lineup than the Lakers, who were missing Andrew Bynum who would have been their starting center.
I disagree with two points here- one, the Lakers shot “so poorly” at 42% against the Celts?!- it should read “so well”- and Duncan having high defense-to-offense rebounding is simply because he plays so much offense- if you were to forbid Duncan from scoring, he would dominate the offensive boards as well