Let's try something different today and start with the conclusion:
An analysis of the rebounding abilities of the NBA's 25 best rebounders' floormates indicates Kendrick Perkins, Damion James, Joakim Noah and Matt Barnes could be underrated rebounders. That same analysis indicates Kevin Love, Jeremy Evans, Landry Fields and Reggie Evans could be overrated rebounders.
Now, how did I get there?
Nature of rebounding
Rebounding is a strange measure. Unlike any other major statistical categories, players actively attempt to accumulate rebounds at the expense of their teammates accumulating rebounds.
Of course, ballhogs exist, but you never see a player actually steal the ball from a teammate in order to score more. Rebounding is different, though. If you can get a rebound, you almost always do. It doesn't matter whether your teammates or opponents are in the way. See ball, get ball.
Therefore, a player will see his rebounding numbers benefit from playing with poor rebounding teammates. Conversely, a player will see rebounding numbers suffer from playing with superior rebounding teammates.
When evaluating players' contributions on the glass, don't evaluate just the players, but also their teams.
To identify a quality rebounder, the first element to consider is whether that player grabs a lot of rebounds himself. Of course, if a quality rebounder plays with teammates who rebound even better than he does, he might not grab many rebounds himself. In a thorough investigation, that's worth exploring. For our purposes, we'll look at just the 25 best rebounders in the NBA.
How did I rank the best rebounders in the league? By how many percentage points each player's total rebound rate was above his position's average, as listed at HoopData. I believe a shooting guard with a rebound rate of 9.0 (average rebound rate for a shooting guard: 7.0) is a more valuable rebounder than a center with a rebound rate of 11.0 (average rebound rate for a center: 14.9).
For each of the NBA's best 25 rebounders (minimum 100 minutes), I charted his rebound rate relative to his position's average. Then, using lineup data from BasketballValue.com, I found the average rebound rate of his floormates (weighted by playing time with the player). The final step was comparing his floormates' rebound rate to the average rebound rate of a lineup (not including that player's position).
For example, the average rebound rate for a power forward is 13.8. An average lineup will post a rebound rate of 50.0.* Therefore, an average power forward's floormates are expected to have a rebound rate of 36.2 (50.0-13.8). If a power forward has a rebound rate of 15.8 and his floormates have a rebound rate of 35.2, the last two columns of the chart would appear: 2.0 and -1.0.
*Using HoopData's average rebound rate for each position gives a lineup with an average rebound rate of 50.5. I'm not sure whether that stems from rounding or not weighting each player by the number of rebounds available while he was on the court, but that shouldn't significantly affect this analysis. I'm not looking for conclusions on rebounders, just indicators.
Here's how the top 25 rebounders and their floormates stack up in total rebound rate above average. The lower the number in the right-most column, the more likely a player is overrated--and the higher, the more like he's underrated.
Kevin Love's floormates' total rebound rate is a whopping 9.6 percentage points below average. Jeremy Evans, Landry Fields and Reggie Evans also play with below-average rebounders, but not to the level of Love. Rebound rate doesn't necessarily overrate them, but there's a distinct possibility it does.
||TRR above average
||Floormates' TRR above average
What about the potentially underrated rebounders on the list? A common thread between them provides a clue about a simpler method for evaluating rebounding.
Eye-test identification of underrated rebounders
The two best rebounders who play with above-average-rebounding floormates are the Bulls' Joakim Noah and the Lakers' Matt Barnes. Who are the two best rebounding teams in the league? You guessed it--the Bulls and Lakers.
Two other players I analyzed--the Magic's Quentin Richardson and the Bulls' Omer Asik--played with floormates with a total rebound rate just 0.1 percentage points below average. As noted, the Bulls have the league's best rebound rate. The Magic rank third.
I don't think it's coincidence that four of the six players most likely to be underrated rebounders play for the best three rebounding teams. It appears logical. For a team to rank highly in rebound rate, it must have good rebounders. The best rebounders on those high-ranking teams will steal rebounds from their teammates, even if the teammates are also capable of rebounding well.
I think this provides a way to evaluate players using the same logic presented in the previous section without running the numbers for each of them.
It wouldn't be a stretch to say anyone who's not the primary rebounder--or for a team that plays its starters and reserves mostly in units, anyone who's not the primary rebounder among the backups--but is a good rebounder on a good rebounding team could be underrated. A quick look at last season's best rebounding teams bears that out.
The Cavaliers led the NBA in total rebound rate, and they experienced a significant roster overhaul during the summer. J.J. Hickson remained on the team, and his rebound rate jumped from 14.1 to a career-high 16.6 this year.
The Grizzlies (second in rebounding last year) didn't see their roster change much, and neither did the Spurs (third in rebounding), although Roger Mason left San Antonio for the Knicks. He's mostly been a flop in New York, but his rebound rate went from 6.3 to a career-high 8.8.
Similar situations occurred with the Magic (fourth in rebound rate). Barnes signed with the Lakers, and his rebound rate climbed from 12.3 to 13,4. Orlando traded Rashard Lewis to the Wizards, and his rebound rate with Washington is his best since he was a 24-year-old Seattle SuperSonic.
Ronnie Brewer, who played for the Jazz (fifth in rebound rate) last year, saw his rebound rate leap from 5.1 to a career-high 8.5 with the Bulls this season. Barnes and Brewer fit the profile of an underrated rebounder last year and this year. I'd definitely keep an eye on them in 2012.
Basically, if you want to get a rough idea of which players might be underrated without running the numbers, this is how you'd look. You might miss candidates like Kendrick Perkins or Damion James, but it's a start.
These numbers point to certain players being underrated rebounders and other being overrated rebounders. The numbers don't say that conclusively, though.
I can't say for certain those who play with above-average-rebounding floormates are underrated and those who play with below-average-rebounding courtmates are overrated. Perhaps, the rebound rates of the potentially underrated rebounders' floormates are inflated by playing with poor rebounders at other times. Maybe the potentially overrated rebounders take all their rebounds from their opponents, and their courtmates are just that bad. I don't know.
But I do know that if I ran a team that was looking for rebounding help, I'd take an extra look anyone with above-average rebounding numbers who played with other above-average rebounders. With teams cutting their budgets and limiting scouting, I'd commit resources to determining whether a trained eye sees rebounding talent that doesn't translate into rebounds--yet--in those players.
It's not a solution, but it's a head start.
Dan Feldman is an author of Basketball Prospectus.
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