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May 21, 2011
Plus or Minus?
Westbrook's Value

by Kevin Pelton


The Oklahoma City Thunder's Game 2 victory over the Dallas Mavericks on Thursday produced a striking statistic that seemed to confirm the storyline that the Thunder won largely because point guard Russell Westbrook spent the entire fourth quarter on the bench. With Westbrook on the floor, Oklahoma City was outscored by 12 points. When backup Eric Maynor was in the game, the Thunder held an 18-point advantage over the Mavericks. Simple comparison, right? Not quite.

In the case of a single game, plus-minus is descriptive but not ascriptive. It tells a factual story--Oklahoma City indisputably played better when Maynor is in the game--yet is unable to trace those results to an individual player. That is why, as great as it is that plus-minus now appears in online boxscores like those on ESPN.com, it must be used with caution.

In fact, in Westbrook's case, plus-minus statistics may not be telling even over a larger sample. According to BasketballValue.com, the Thunder was 8.1 points worse per 100 possessions with Westbrook on the floor this season, the worst net plus-minus among the team's rotation players. Meanwhile, Maynor had the team's second-best net plus-minus at +8.2 points per 100 possessions.

However, it would be reckless to think that the Thunder are better off with Maynor running the point in place of Westbrook. In fact, there's evidence showing that Westbrook produces much better results than Maynor with the players who were on the floor with the backup point guard during the fourth quarter of Game 2's win.

The problem is that Scott Brooks' rotations made it difficult to compare the two players statistically. For much of the season, three of Oklahoma City's best players came off the bench. Serge Ibaka moved into the starting lineup at midseason after Jeff Green and Nenad Krstic were traded to the Boston Celtics for Kendrick Perkins and Nate Robinson, but Nick Collison and James Harden are still part of the Thunder's dangerous second unit while Westbrook is part of a less effective starting lineup.

A comparison of how frequently teammates have been on the floor with each point guard as a percentage of their total possessions shows how different the lineups Maynor and Westbrook play with truly are.

Teammate    Westbrook   Maynor
Sefolosha     .656       .206
Durant        .936       .393
Ibaka         .580       .481
Perkins       .152       .007
Harden        .401       .882
Cook          .056       .349
Collison      .262       .641
Mohammed      .058       .194

Collison, Harden and Ibaka tend to move between the two lineups, but Kendrick Perkins and Thabo Sefolosha have played almost exclusively with Westbrook and Daequan Cook and Nazr Mohammed are almost on the floor at the same time as Maynor. Even Collison and Harden played far more frequently with Maynor. The distinction between the two units shows how difficult it is to consider Maynor and Westbrook individually. Any attempt to compare them inevitably turns into a look at the Oklahoma City starters and the team's bench.

That's instructive in terms of understanding what happened in the fourth quarter of Game 2. It's misleading to say Westbrook was benched without considering the fact that so too were the rest of the Thunder's starters, save Durant. Collison and Harden finishing games has become the norm, but for Brooks to continue with Cook in the game instead of going back to a starter suggests he was riding a hot lineup more than punishing Westbrook.

So is it possible to separate the influence of Oklahoma City's rotation from the two point guards? One solution is to compare lineups where the other four players on the floor are the same. Again, the distinction between the Thunder's units makes this challenging. There are just five lineups that played at least 40 possessions with both point guards. Of these, four played better with Westbrook at the point.

                                    Westbrook        Maynor
Lineup                             Pos     Net    Pos     Net
Harden/Durant/Ibaka/Collison       308   +13.6    228   +12.3
Harden/Durant/Green/Ibaka          305   - 8.4     46   -12.0
Harden/Durant/Collison/Mohammed     71   +22.5     78   +21.7
Harden/Cook/Durant/Collison         64   +12.5     48   -14.6
Harden/Cook/Durant/Ibaka            49   -38.0     54   +24.1

Oddly, the lineup that finished off the Mavericks in Game 2--Maynor, Harden, Cook, Durant and Collison--was horrible during the regular season, getting outscored by 14.6 points per 100 possessions. Replace Maynor with Westbrook and the same group was positive. These lineups played so little that their ratings are not reliable individually, but taken together they show Westbrook was better than Maynor.

In the playoffs, the evidence for Westbrook's value is even stronger despite the fact that Oklahoma City has been slightly worse with him on the floor. Again, Collison and Harden have made an enormous impact on the Thunder's fortunes. Collison's postseason net plus-minus of +20.3 points per 100 possessions is off the charts. As a result, it's important not to give Maynor too much credit for getting to play with effective reserves.

Looking strictly at lineups that feature Collison, Durant and Harden, Oklahoma City has been dominant with Westbrook at the point, outscoring opponents by 19.3 points per 100 possessions. By contrast, those three players plus Maynor have been only slightly better than break-even (+2.5 points per 100 possessions). The difference is the scoring punch Westbrook provides. When he's played with the Thunder's three other best players, the team has averaged a sizzling 122.1 points per 100 possessions. With Maynor and the same group, Oklahoma City's offensive rating drops to 108.7.

The decision Brooks made to leave Maynor and his other reserves in the game made sense because Maynor was playing well and the unit had established momentum that paid off down the stretch. Don't confuse that with the Thunder being better off without Westbrook in general. When he gets the chance to play with Collison, Durant and Harden, Oklahoma City is truly an elite team.

A version of this story originally appeared on ESPN Insider Insider.

Kevin Pelton is an author of Basketball Prospectus. You can contact Kevin by clicking here or click here to see Kevin's other articles.

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