A “So What?” to Arms

For those who are utterly exhausted from the first couple days of free agency, and need a breather from contracts, mid-level exceptions, player options, Bird Rights and salary caps, enjoy this brief distraction from the chaos.

The 2015 NBA Draft has come and gone and many of the annual traditions that fans have come to expect and cherish were honored:

• Outrageous, cringe-worthy fashion choices:

• Uncomfortable embraces between the commissioner and new millionaires:

• The New York fans’ apocalyptic reaction to whichever poor soul the Knicks select:

• The Joel Embiid-like reaction to hearing that your next season will be spent in Philadelphia:

Perhaps the most reliable tradition on display Thursday night was the player analysis of Jay Bilas and his annual marveling at the length of teenagers’ arms. In any other profession this sort of long-armed fixation would be considered odd, if not perverse. Lucky for Bilas, he chose a line of work that enables his fetish in a socially acceptable manner. Granted, it was far more fun before Bilas was in on the joke. Now, sometimes when JB brings up wingspan, he uses a tongue-in-cheek self-awareness that he never used to exhibit. Bilas even acknowledged the most popular NBA Draft drinking game when fans at home drink each time Bilas mentions wingspan:

On the surface, it’s understandable why having long arms would benefit a basketball player. Defensively it’s a no-brainer: players can use their long arms to defend on the ball, block shots, swipe at steals, sneak into passing lanes to deflect passes and rebound opponents’ errant attempts. Offensively, a player could use go-go gadget arms to snag offensive rebounds and get put backs (Tristan Thompson) or use a high release to make a contested post move or jump shot less difficult (Rasheed Wallace / Kevin Garnett).

But, is the collective obsession with wingspans justified by statistics? Does a correlation exist between measured player performance and the relative length of their arms? Does having longer arms actually help a player get to the top of the sport? To find out, I first had to select a statistic to measure player performance. I chose John Hollinger’s well-known Player Efficiency Rating (PER). To be eligible, a player must have played in at least 55 games and recorded over 1200 minutes over the course of 2014-2015 season (~15 mins/game for all 82 games). There are undoubtedly a number of limitations to using PER, but no statistic is perfect. Also, any stat that says these six guys were the best players from this past season is good enough for me:

Next, I had to find the right measurement for wingspan. I wanted to reward shorter players with long wingspans relative to their height. For example, Dwyane Wade stands at 6' 3.75" without shoes, but boasts a wingspan of 6' 10.75". Chris Kaman, on the other hand, stands at 6' 11.5" and has a wingspan of the same - 6' 11.5". From a statistical standpoint, Kaman has a longer wingspan, but whose is more impressive? Wade’s. To account for this, I used “wingspan ratio” (Wingspan / Height without shoes) as the measurement for wingspan.

When examining the relationship between PER and Wingspan Ratio, I compared players with the highest PERs in the league to those with the lowest PERs. Conventional wisdom says that if wingspan is as important as Bilas believes it is, the players with the highest PERs would have longer wingspan ratios, as a whole, when compared to those with the worst PERs. Using a sample of 64 players, here is what I found (all wingspan data was taken from the NBA Combine via Draftexpress):

The high PER cluster and the low PER cluster might as well be mirror images of each other. It is evident that there is no real correlation between wingspan and high PERs per this study. One thing that stood out to me, though, was that the player with the highest wingspan ratio also happens to be the Defensive Player of the Year, Kawhi Leonard. One of the noted limitations of PER is that it does not appropriately factor in the defensive side of the ball. Plus, most of the potential benefits for having a long wingspan manifest themselves on defense. That is why I decided to test a different question. Is there a relationship between wingspan and defensive ability?

The statistic I chose to represent defensive ability was Defensive Win Shares – an estimate of the number of wins contributed by a player due to his defense. Take a look at the wingspan ratios of players with the most Defensive Win Shares when compared to the players with the least:

This visual clearly tells us a different story than the PER graph. The players with more Defensive Win Shares, by and large, have greater wingspan ratios than those at the bottom of that statistic. For comparison, 16 players with the least Defensive Win Shares (half of the sample) have wingspan ratios under 1.04. Meanwhile, only two outliers from the elite group of defenders have wingspan ratios below that level (Steph Curry and Marc Gasol). Conversely, there are no players in the bottom group with wingspans over 1.1; meanwhile, six different players from the top group boast wingspans above that number - including Kawhi Leonard and DeAndre Jordan.

It would appear that a player’s height to wingspan ratio is not overly important when it comes to PER, and to extrapolate, offense in general. However, the notion that wingspan is a significant consideration when projecting a player’s defensive potential is supported by this remarkably unscientific experiment. I wouldn’t say this is a San Andreas-like groundbreaking conclusion (you thought I was going to go with The Rock’s movie, didn’t you?), but next year when I’m playing the Jay Bilas drinking game, I’ll feel better knowing that wingspan actually does matter. Next stop – MIT Sloan Sports Analytics Conference!

Now go refresh your twitter feed because I think Rondo just signed with your favorite team.

#NBA #NBAFreeAgency #TomPiccolo