By Julian Ryan
As the Oklahoma City Thunder head into the playoffs, the team remarkably has both of the highest usage players in the league this season: Russell Westbrook and Kevin Durant. Both players are obvious superstars and when they have been on the floor together this season, they have been responsible for ending almost two-thirds of their team’s possessions.
However, an enduring narrative of the team over the last couple of seasons has been that Westbrook does more harm than good for the team by taking shots away from the almost-certain MVP Durant. Because of Westbrook’s injuries this season, we have a natural experiment of treating OKC with Westbrook versus the control without Westbrook and can compare those two teams to see if there is any truth to that statement. Before that though consider the performance of Durant with and without his fellow all-star.
| USG% | TS% | ORtg | DRtg | GameScore | |
| With Westbrook | 31.2 | 0.643 | 124.7 | 104.5 | 24.5 |
| Without Westbrook | 35.4 | 0.651 | 123.4 | 104.1 | 25.2 |
HSAC has already given some lip service to why Durant is pure awesome but the table above is another opportunity. With Westbrook out, Durant was able to significantly increase his usage rate without compromising efficiency elsewhere, another reason why he is the deserving MVP this season. It also suggests that potentially Durant is stifled when Westbrook is playing and would be able to take more shots at an equally efficient rate if Westbrook didn’t hog so much.
However, the myth that the Thunder are better without Westbrook is patently false.
| Win Percentage | Point Differential | Adjusted Point Differential | Number of Games | |
| With Westbrook | 0.745 | +6.84 | +7.61 | 47 |
| Without Westbrook | 0.686 | +5.11 | +4.60 | 35 |
Westbrook may be take some shots away from Durant, but his efforts are still at an elite level and the shots he takes away from the rest of the team and replaces at a higher level outweigh that effect. Comparing adjusted point differentials, a t-test suggests that there is a 0.27 chance that the improvement is random, but there is certainly no evidence to suggest that the Thunder are worse.
While the Thunder improve with Westbrook healthy, is he still taking too many possession? Amongst the games in which Westbrook played, let us compare when Durant had a higher usage rate than his partner in crime and vice-versa.
| Win Percentage | Point Differential | Adjusted Point Differential | Number of Games | |
| Westbrook > Durant | 0.710 | +5.81 | +5.99 | 31 |
| Durant > Westbrook | 0.800 | +9.00 | +10.96 | 15 |
A t-test on opponent-adjusted point differentials gives a p-value of 0.12 of rejecting the null hypothesis that the Thunder are equally good whether Durant uses more possessions than Westbrook or not. It’s not certainly significant but is indicative that the Thunder are better when Durant dominates over Westbrook.
There is an issue of selection bias in that Durant/Westbrook may shoot more when playing well skewing our results. However, Durant’s average gamescore (a game-by-game analog to PER) is almost identical whether using more possessions than Westbrook or not. It is 24.3 with Westbrook dominating and 24.9 with Durant using more of the ball. Westbrook’s average gamescore does drop from 17.1 to 15.7 when Durant dominates. However, the probability that the drop is random is 0.46, far from statistically significant.
In general, both players perform at similar levels regardless of who is taking more possessions, but the Thunder perform better when Durant is the dominant force. Overall then, Westbrook is a net positive on the team as clearly seen when the team was unable to compete after he went down in the playoffs last season; however, when you are playing with the league MVP, you should not have the highest usage rate in the league. OKC beating opponents by 9 points a game when Durant took more possessions than Westbrook is a number that would have led the league over the course of the season. If Scott Brooks can unlock that formula for the playoffs and get Westbrook to play second banana, the Thunder will be a very tough team to beat.
