Nylon Calculus: Does wingspan really make a good defender?

A couple of weeks ago I had written about taking Ed Weiland’s draft standards into the modern era and had thought to add wingspan differential as a way to round out a college prospect’s defensive potential. Outside of DBPM, there might not be a better statistic that gives us a guarantee for defensive success at the NBA level.

Size is nice though, isn’t it? If a player with great length, reach, or wingspan differential comes along, one would like to assume that a solid coaching system at the very least could turn that player into a solid defender.

My initial question was: Does wingspan actually contribute to positive defensive contributions in games? The short answer is no, but by diving into correlations we should find the real reason behind what makes the foundations of a solid defense.

Analyzing all players in the 2017-18 NBA season, I subjectively selected various statistics that are conceivably related to having a long wingspan and measured their correlations against each other. You’ll see what I mean in the table below.

In order to help understand the findings in my initial correlational analysis by correlograms, I then plotted data on a network plot to help understand what the most important contributing defensive attributes. The network plots give us better visibility as to which statistics seem to be most closely related. Sources of each data point are linked in the following table.

What matters for bigs?

For big men in the NBA, height matters more than wingspan differential and it makes sense. If a player is already tall, then the impact of any extra inch of wingspan is negligible. Deflections, lunging for loose balls, and contesting shots all have clear correlations to Defensive Win Shares and to a lesser degree DBPM and DPIPM. What jumps out the most is how strong of a correlation that distance traveled per game has to Defensive Win Shares, and to a lesser degree DBPM and DPIPM.

Understanding that wingspan differential doesn’t correlate strongly, defensive contribution most probably comes from a willingness to move. To drive this point home, Mo Bamba’s defensive production at the next level may be more driven by his elite mobility than his wingspan.

You’ll notice the various correlations grouped by relatability in the graph above. For example, in the upper left, blocks, height, and wingspan differential are most closely related to each other by their respective correlations. We can use both graphs to ascertain the following for bigs in the NBA: distance traveled on defense per game, leads to a high volume of contested shots, grabbing loose balls, and thus per game Defensive Win Shares. In addition, the higher the number of contested shots per game lead to a higher DBPM. Notice that while the taller height of a player can lead to more blocks and contested 2-point shots, a longer wingspan is probably not contributing too much of anything.

Average defensive speed contributes relatively strongly to defensive rating, defensive rebounding percentage and to a lesser extent DBPM, but doesn’t at all in regards to contesting shots. This could be understood as a big man just being a general deterrent when he quickly gets to his spot in the halfcourt or on the fast break.

Perimeter players and wingspan

This looks eerily similar for those on bigs. Wingspan differential does a little bit better here, but not significantly enough. Height correlates more strongly to defensive rebounding than for bigs. Average defensive speed in a game correlates okay with DBPM and to a far lesser degree DPIPM, but it doesn’t matter at all when considering Defensive Win Shares. Notice again, the distance a player travels on the defensive end in a game correlates strongly to Defensive Win Shares contributed in a game, but less so for DPIPM.

For the most part, perimeter players and big men have similar correlations. The correlations between wingspan and other contributions are near nonexistent, but correlations between distance traveled on defense and other contributions remain strong. There’s definitely something to perimeter players and covering distance consistently.

Point guards and wingspan

For point guards, wingspan still doesn’t correlate to contributing strongly to any advanced metric. Having a larger wingspan barely correlates strongly for being able to contest shots. Height becomes a stronger correlation to contesting shots and grabbing rebounds. At this point, average defensive speed per game remains a little less significant.

Here you can see that average speed defensively has some relation to loose balls per game, but not necessarily much else. Getting mileage in on defense for point guards means that they’re actively chasing their counterparts and making sure there’s a body on them at all times. Although the data for distance above is scaled per game and not per minute, we can still get a sense of what a good defending point guard is in the NBA. For what it’s worth, Lonzo Ball will run 1.18 miles on defense in a game compared to Jose Calderon’s .55 miles.

Considering Lonzo Ball’s development, the Ball family included running as a part of the training regimen. In fact, Lavar Ball had his sons “run like deer” to the point that their sons could overcome any in-game deficiencies because “their conditioning was so high.”

To be clear, Lonzo Ball’s wingspan differential is just a touch below average. He’s pretty tall for a guard, but it’s not like he’s some physical wunderkind. Players like Ben Simmons and Steph Curry also have below average wingspan differentials but are pretty solid defensively. All three players though run more than 1.12 miles per game just on the defensive side of the ball.

It’s probably time to put any wingspan narrative to bed, as it seems to have little correlation with any other statistic available for analysis. Even height seems to have little correlation with positive defensive performance, but deeper analysis on relative height advantage could be a better way to understand how height works on the defensive end of the floor.

Krishna Narsu points out that “the idea of how best to defend a 3-pointer has become pretty solid — don’t let your opponents shoot them.” He posits that it’s most important for a defender to make their opponent feel so uncomfortable that they’d start missing shots. As shown by the plots above, this definitely seems to be the case.

Though disruption might not necessarily be characterized by a 6-foot-6 forward with a 7-foot-4 wingspan, I’d argue that disruption is most characterized by consistent running enfolded by the old coaching cliché of “getting to your spot” on defense. “Disruption” or hustle seems to be defined as covering distance consistently over the course of an NBA game in order to contest shots, deflect passes, and grab loose balls. As seen above, a player isn’t required to be super fast either.

How does one “produce” disruption? Further analysis would have to be done, but I’d involve some measure of coaching, franchise stability, and overall player’s desire to run. Evaluating disruption from the collegiate level is a little more difficult since the game is so dependent on the zone and we might not get a clear understanding of what good defensive recruit looks like as a result, even if tracking data was available for college players.

Next: The Rockets in free agency and the MOREY score

For players, it stinks to run on defense since it takes a huge physical toll, and there’s only so many players that can get themselves motivated to keep up defensive intensity like Paul George or Giannis Antetokounmpo. These players probably have grown in environments where they’ve learned to love running. Or more simply, they’ve received exceptional defensive coaching, to the tune of Hubie Brown. If you watch the video, then good defense and covering distance going hand in hand makes sense. Forcing opponents to the short corner on the defensive end instead of the middle prevents high percentage shots, but causes plays to drag out if that player dribbles the ball back out. Teaching not to foul perimeter players helps elongate plays as well, but both signal that the defensive player is doing his job. Players will also cover more distance if they hustle on fast breaks.

So in short, if you’re a kid with NBA dreams, then get to running a couple of miles every day, or get to running suicides. “Freakish size” isn’t needed when fundamentals and conditioning are in top shape.