How important are guards to rebounding? That's the question I've been pondering since last week, when David Locke and I discussed the Utah Jazz's poor defensive rebounding on our regular Mythbusters podcast. It turns out Utah's big men aren't the culprits, other than Enes Kanter. The problem lies largely with the backcourt of Randy Foye and Mo Williams, both of whom are grabbing fewer than four percent of available rebounds while on the floor.
Such a combination is rare, though not necessarily as historic as I originally suspected. The most recent team to play two guards so weak on the glass was actually ... last year's Utah Jazz, when Raja Bell started next to Devin Harris. However, just two other teams in the last decade have had two regular players with rebound rates worse than four percent: the 2007-08 Charlotte Bobcats (Earl Boykins and Jeff McInnis) and the 2008-09 Minnesota Timberwolves (Bobby Brown, who was acquired at the trade deadline, and Sebastian Telfair).
The example of the Jazz made me curious as to the relative importance of various positions to team's overall rebounding success or failure. From a purely statistical standpoint, every rebound is equally important. However, that doesn't necessarily translate at the team level in large part because the variability between the best and worst rebounding big men is much larger than the spread among guards.
To study the issue, I used 82games.com's data on production by position to find how many rebounds teams are getting from each spot this season. Here are those figures, normalized for available rebounds:
Neither of Utah's guard spots is worst in the league individually, though together their rebound percentages (9.2 percent) are tied with Brooklyn for last. Every other team in the NBA has its backcourt grab at least 10 percent of available rebounds. Thanks to Reggie Evans and Kris Humphries, the Nets' power forwards are the only position group in the league that surpasses the 20 percent mark, with Cleveland's centers (18.8 percent) in second behind Anderson Varejao's exploits on the glass.
While it's easy to determine that the average basketball player has a rebound rate of 10 percent, the average varies widely by position. The typical point guard is at 5.5 percent, with shooting guards at 6.3 percent, small forwards 8.8 percent, power forwards 13.9 percent and centers leading the way at 15.5 percent.
As to the original question, this year's data offers a somewhat surprising answer. Not only is rebounding from the point guard spot not helpful in terms of overall team rebounding, it's actually a negative factor. Here are the correlations with team rebound percentage for each position:
Indeed, big men prove much more important to team rebounding. One partial-season's worth of data isn't enough to suggest that power forwards really make a larger difference on the glass than centers, though it is an interesting observation. More importantly, the numbers don't actually indicate that the worst thing a team can do on the boards is have a point guard that rebounds effectively.
There are a handful of issues with drawing that conclusion. For one, 82games.com's numbers did not allow me to distinguish between offensive rebounding and defensive rebounding, and at the team level those are often unrelated skills because of the influence coaches have on whether their teams choose to crash the glass or get back on defense. Much of the negative correlation comes from the Boston Celtics, who pair an elite rebounder at point guard in Rajon Rondo with the league's worst rebound percentage. That figure stems entirely from the offensive end, where the Celtics are historically bad. They rank sixth in the league in defensive rebounding.
Intriguingly, the Jazz is another team that suffers from combining the two ends. Utah's rebounding problems are entirely on defense, where the team ranks 29th of 30 teams. The Jazz is fifth in offensive rebounding, and because there is more variation in team rebound rates at the offensive end, Utah's overall rebound percentage is actually better than average.
Beyond that, there is more crossover than this simple analysis can address. Because of the high diminishing returns to defensive rebounding, point guards that get a lot of rebounds may be doing so in large part because there are more to go around due to teammates that are allergic to the glass.
So feel free to pick up that point guard who loves to rebound. At the same time, the example of this year's Utah squad aside, a backcourt that doesn't hit the glass probably isn't worth much worry.
Kevin Pelton is an author of Basketball Prospectus.
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