Russell Westbrook and Passing Efficiency

It’s natural for us to maintain a healthy skepticism about Russell Westbrook’s NBA-leading 10.3 assists per game. For one thing, it’s a small sample size, and there are plenty of games left in the season for Chris Paul, John Wall, and other point guards to catch up. For another, Westbrook’s numbers are buoyed by the return of Kevin Durant, who receives a third of his passes and makes over half of the shots that flow from them. These caveats are sensible, as is the general idea that assists are insufficient measures of how a player facilitates an offense.

But there are other metrics that enhance our understanding of playmaker contributions, and they happen to shed a positive light on Westbrook, too. For example, last Friday, Seth Partnow noted that the Thunder guard ranks among the top three in playmaking usage. When Westbrook creates opportunities for his teammates, they have an effective field goal percentage that’s ten points higher than league average.

Another helpful angle is Passing Efficiency. As Andrew Johnson discussed last year, the percentage of assists, secondary assists, and free throw assists that stem from a player’s passes is associated with higher offensive efficiency.[1. As Andrew pointed out in his post, the concept of “passing efficiency” has been studied quite a bit. The literature includes works by Aqeel Phillips, Nick Neuteufel, and many others, and I am indebted to them.] If we look at an “adjusted” version of this metric that incorporates potential assists, we get a broader sense of the scoring opportunities that a player creates for his teammates.[2. Again, this concept is nothing new. I use the term “Adjusted Passing Efficiency” here simply to convey that it builds off of Andrew’s definition. If it proves to be a useful metric, it might require a different name.] On both fronts, Westbrook does well.

Among players with at least 500 completed passes, Westbrook has the highest Passing Efficiency. Nearly a quarter of his passes contribute to points in some form, outpacing his closest competitor by about seven percentage points. Even more notably, his 57 percent Adjusted Passing Efficiency is ahead by approximately 16 percentage points.[3. All of the data come from NBA.com/Stats. Note that the “AST to Pass% Adj” column is what we’re calling “Passing Efficiency” here: (Assists + Free Throw Assists + Secondary Assists) / Passes Made. “Adjusted Passing Efficiency” adds potential assists to the numerator: (Assists + Free Throw Assists + Secondary Assists + Potential Assists) / Passes Made.] Westbrook might make fewer passes than his peers do, but his ball distribution has the effect of being relatively more purposeful and impactful.

As you might expect, these numbers represent an increase from previous years:

At the moment, Westbrook is about 5 percentage points higher in Passing Efficiency and roughly 10 percentage points higher in Adjusted Passing Efficiency. These increases apply even when we break down last year’s numbers by Durant’s availability, since the results were essentially the same in games that he played and games that he missed.[4. During the 2014-15 season, in games that Durant played, Westbrook had a Passing Efficiency of 17.8 percent and an Adjusted Passing Efficiency of 46.3 percent. In games that Durant missed, Westbrook had a Passing Efficiency of 18.9 percent and an Adjusted Passing Efficiency of 46.6 percent.]

Although Westbrook is clearly off to a strong start, three salient points are worth emphasizing.

First, his numbers are likely to come down as the season progresses. Over the past couple of years, among players with at least 3,500 completed passes, the top Passing Efficiency was at 20 percent and the top Adjusted Passing Efficiency at 51 percent (with Ty Lawson dominating in this latter category). Westbrook may still end up on the leaderboards, but perhaps not at the lofty levels where he presently resides.

Second, it remains challenging to differentiate between individual skill and offensive system. Oklahoma City is currently near the bottom of the league in made passes, and it compiled the fifth lowest totals in both the 2013-14 and 2014-15 seasons. Apart from last year’s mediocre showing, it’s had some of the better efficiency numbers, too. This topic alone probably warrants its own study, but one wonders how much of Westbrook’s results are driven by team priorities and, conversely, how much of OKC’s results are a function of playing to his strengths.

Lastly, efficiency numbers leave some key questions unanswered. They don’t, for example, shed light on what Alex Lee calls “Assist Quality.” They also don’t tell us where Westbrook lies in the Thunder’s PASS Network. So it’s essential to view Passing Efficiency within a broader set of data points that collectively reflect playmaking ability.