NBA HD: Does Effective Height Have an Effect?

Height is one of the most sought after commodities in the game.  Being taller than your opponents helps grab a live ball, get a shot off cleanly, and block shots.  But there’s more to length than being tall head to toe.  A player’s wingspan, vertical leap, and reaction time can make a “shorter” athlete play several inches taller than his height.

More and more teams are employing “small ball” lineups that try to gain an edge by emphasizing speed and quickness over height.  On the other hand, you have teams like the Lakers who can throw three 7-footers at the opponent without missing a step.  So how important is height for a team?

In today’s post, I wanted to look at the relationship between team height and rebounding.  To do this, I gathered the heights of every player that played in the NBA this season and grouped them by their respective team.  Instead of calculating the average height for each team, I weighted the team heights by minutes played.  This adjustment eliminates the bench bias for teams that employed guys like 7-2 Primoz Brezec who rode the pine all year (Philly and Milwaukee).  I’m not calling you a tall team if the players on the court aren’t tall.

After calculating the minutes-weighted height (or effective height), I compared the team length to their rebounding rates.  So, who’s the tallest team in the NBA?

The Sacramento Kings ran the tallest team in the NBA this year with an effective height of about six-foot eight.  Much of their lofty ranking comes from Donte Green who stands 6-11 at the small forward position. In fact, the most common lineup in the Kings system this year was Beno Udrih( 6-3) – Tyreke Evans (6-6) – Donte Green (6-11) – Carl Landry (6-9) – Spencer Hawes (7-0) [have to give an assist finger point to Aaron Barzilai of basketballvalue.com fame].  The third most common lineup could touch the sky with Donte Green playing at the two and Tyreke Evans running the show.  To round out their rotation, the Kings also have 6-9 Omri Casspi to play the three and 6-11 Jason Thompson to play the four.  That’s a tall team.

Despite being really long, the Kings didn’t rebound any better overall than the average team (50.4 TRB%).  That’s largely because Donte Green has arguably been the weakest 6-11 rebounder to get big minutes in the NBA of all time.  A premature superlative?  Possibly. But just remember that his 7.8 percent career total rebound rate is the lowest among any 6-11 or taller player to play at least 100 games in the NBA.   Moreover, Spencer Hawes fits the mold of a shooter who just happens to be extremely tall and doesn’t rebound nearly as well as his center contemporaries.  His teammate Jon Brockman grabs twice as many offensive boards as he does despite boasting the height of a typical shooting guard.  Actually, the team’s above-average offensive rebounding rate could be attributed solely to Brockman’s knack for collecting his team’s missed shots.

You’ll notice that three of the five tallest teams in effective height have pedestrian rebounding rates.  Not coincidentally, each of them (Kings, Suns, and Raptors) like to have a stretch 5 on the floor at the expense of collecting boards.

And the shortest teams? Well, the Warriors employ Nellie-ball which takes small-ball to the extreme.  Several of their most used lineups included Corey Maggette at the four spot which would get any normal coach fired.  But Don Nelson isn’t just any coach– he has over 1,000 losses on his resume.  Contrast the rebounding rates of Golden State to Houston who lost their resident redwood Yao Ming in the offseason.  Despite having the second smallest team in the NBA, they rank very nicely amongst their NBA competitors and about the same as the Toronto Raptors.

To draw a better picture, I’ve included three graphs that chart effective height against their rebounding rates.  Each chart includes a trend-line in red.

As you can see, I broke up the plot area into quadrants to help interpret the orientation a bit better. You can see how well the Spurs rebounded this year despite having one of the shortest effective heights in the league.  That, my friends, is the power of DeJuan Blair.  Blair has vertically-challenged rebounding abilities unseen since Danny Fortson.

If you haven’t figured out already, you don’t want to be in the top-left quadrant.  That area’s reserved for the teams who try to stretch the floor with their height but often lose the battle for live balls.  It’s no surprise that each of these teams (NJN, IND, NYK, WAS, MIN, and TOR) lost more games than they won.

This year, the correlation between eHt and TRB% was .33 which means that there’s a decent relationship between the two entities.  30 teams isn’t a big sample size, to be sure.  Aside from the numbers, there’s much  more to rebounding than height.  As I mentioned earlier, physical attributes like wingspan and vertical have an effect in addition to more mental qualities like positioning and reaction time.

But let’s go further and separate rebounding into two parts: offense and defense.

Here’s offensive rebounding rate and how it relates to effective height.

Offensive rebounding and effective height have a much stronger relationship than overall rebounding– the correlation in this (small) sample was .42.  A one inch increase in effective height translates to about a two percent uptick in offensive rebound percentage (say 24 percent to 26 percent).  Perhaps with more defenders in the lane to rebound the ball, height gives you that extra edge needed to steal a board.

Of course, as the Pacers can attest, sometimes height matters nothing.  I mean, 7-2 Roy Hibbert grabs fewer offensive boards than Chuck Hayes who is eight inches shorter.  To reiterate, a big vertical can close the gap underneath and Hibbert’s ineptitude demonstrates this quite nicely.  Moreover, their power forward Troy Murphy slings it from the perimeter and therefore, rarely gets in position to grab offensive boards.  The Pacers can trot out a tall team but it doesn’t mean they’ll play tall.

However, this seems to be the exception more than the rule.  It’s very hard to get offensive rebounds with a short team.  As much as it is a height issue, it’s probably also a product of strategy.  If I’m coaching a short team, I’m more often than not sending my players back to defense on the shot release since it’s a longshot that they’d collect an offensive board anyway.  Houston and Philly do this better than anyone but they still aren’t quite elite.

Here’s where it gets interesting. On the defensive end, it doesn’t seem to make a difference whether you’re a tall team or not.  The relationship is essentially random with a correlation of -0.03.  Check it out.

I wouldn’t pay too much attention to the negative trend-line as the relationship is about nil and the sample size isn’t enormous.  Phoenix and Cleveland have about the same effective height this season but 27 teams separate them in defensive rebounding rate.   Sacramento has the tallest team but they rebound no better than average and Houston, as small as they are, actual rebounds better on the defensive end.  Golden State still rebounds worse than a lightweight suffering from a Franzia hangover.

Why is it random? An extra rebounder matters more than an extra inch.  On defense, it’s common to have all five defenders waiting for the ball so the individual height advantage tends to vanish.  Of course, there will always be matchups where this isn’t the case but on the whole, defensive rebounding isn’t sensitive to height differences with a full five eyeing the rebound.

With lineup data available, a logical next step might be to see how much height matters in the play-by-plays.  Not just for one team but on a matchup level too.  How much does a couple inches of height matter against a tiny squad like the Warriors? How about versus the Kings?  Also, going back further years would give this study a huge boost (if someone hasn’t done that already).   For now, the main takeaway is that tall teams benefited from their height advantage most on the offensive boards and not on the defensive end.