Impact Percentage: A New NBA Fingerprint

No two teams in the NBA are alike when it comes to the mixture of player tendencies, lineup combinations and styles of play. One metric that tells a story of player involvement (and furthermore, can serve as a team’s fingerprint) is usage percentage. This estimates the portion of team plays used by a player while he was on the floor. In other words, it shows us how often a player ends his team’s possessions. Players like Russell Westbrook, DeMarcus Cousins, and DeMar DeRozan currently lead the league in usage percentage.

Using our revolutionary STATS SportVU data, we have recently developed an improvement upon traditional usage percentage. Now, not only can we tell how frequently a player terminates a possession (with a FGA, FTA, or Turnover), but we can also quantify how often they impact a possession (with a drive, a ball screen, an isolation or a post up). We’ve appropriately named this value impact percentage.

Why is this valuable? Consider players like Goran Dragic and Mike Conley, who rank 38th and 49th, respectively, in usage. Although a glance at these numbers might persuade one to think that these two aren’t chief possession-influencers, they are both among the top 10 in the league in impact percentage.

This new statistic was mentioned in ESPN the Magazine’s newest analytics issue, which hit the stands on March 17. Today, we are going to use it to analyze Monday’s matchup between Oklahoma City and Golden State.

As mentioned earlier, Russell Westbrook leads the NBA in usage percentage – but he also sits at the top of the leaderboard in impact percentage. When you look at OKC exclusively, no one comes close to the amount of impact that Westbrook has on their possessions.

ImpactPercentage

Usage plays a part here, but when you break down OKC’s SportVU plays – drives, isolations, post ups, and ball screens – it’s evident that these are where the bulk of Westbrook’s impact lies. Westbrook accounts for over 51 impactful plays per game on average. The next closest Thunder player is Victor Oladipo at 16.

ImpactPlays_OKC

Let’s talk about variability. In statistics, standard deviation measures how spread out a distribution is. A low standard deviation tells us that most of the numbers in a sample are close to the sample’s average – in other words, there isn’t much spread. A high standard deviation tells us that the numbers are more scattered. Unsurprisingly, due to Westbrook’s outlandish numbers, OKC has a very high standard deviation when considering impact percentage.

The Thunder’s standard deviation comes to a whopping 15 percent. In comparison, Golden State, before Kevin Durant’s MCL sprain on February 28th, had a standard deviation of 8 percent.

ImpactPercentage_standard-deviation

The biggest and most obvious takeaway here is that these are two completely diverse teams when it comes to how the ball is facilitated, and further, who the offense revolves around. Yet, a deeper dive into the Warriors’ Impact numbers reveals that they’ve had to adjust their strategy in KD’s recent absence.

ImpactPercentage_KD-Table

Steph Curry’s impact percentage has increased from an already team-leading 49 percent to an even higher 55 percent while Klay Thompson’s has shot from 31 to 37. This is all expected. What’s more compelling, though, is how a guy like Ian Clark is doing exponentially more with his limited minutes.

In his first eight games* since Durant’s injury, Clark has nearly doubled his ball screen usage (2.6 to 4.8 per game) and increased his drives (1.2 to 1.9 per game). On top of that, his minutes slightly decreased – even with him playing 34 minutes March 11 against the Spurs as Steve Kerr rested all his stars.

It’s important to mention that impact percentage is not necessarily a reflection of efficiency. Just because a player is influencing his on-court possessions doesn’t mean that he’s influencing them positively. It’s no secret that the Warriors are struggling to fill Durant’s shoes, especially when it comes to productivity – but it does appear as if guys are at least stepping up to the challenge and getting involved.

With all of this in mind, it’ll be interesting to see how OKC handles a Golden State team that finally seems to be adjusting to Durant’s absence.

*all numbers are as of 3/17/17

Photo By: AP Photo/Alonzo Adams
Illustration By: STATS/Andrew Skweres