Baron Davis and the Clippers

With the NBA off-season now in full swing, I thought it a good time to apply a relatively new tool to the purpose of evaluating off-season transactions. That tool is adjusted plus-minus! For those not in the know, I recommend starting here and here for the most recent adjusted plus-minus data and to explain a little about what it is. For those who don't want to click, I will give a brief summary.

The plus-minus statistic by itself measures a very simple, yet enlightening phenomenon. If the Cavs outscore the Celtics by 8 points when LeBron James is on the court but are outscored by 16 points when he is off the court, LeBron gets a plus-minus of +24, reflecting the team's vastly superior performance when he is on the court. The problem is that if LeBron's teammates are poor, his plus-minus will be higher than if he played on a stronger team. Another problem is that a player who is on the court at the same time as LeBron might take undue credit for what were LeBron's positive contributions. What adjusted plus-minus does is to incorporate a multiple regression analysis that accounts for the quality of a player's teammates in computing plus-minus. Although subject to some high standard errors, using two or more seasons' worth of data gives a fairly accurate estimate of the values of each player in the NBA.

What a tool like adjusted plus-minus can allow us to do most readily is to see exactly how a move like the Clippers' signing of Baron Davis can impact the team's win-loss total. Below is a projected lineup for next year's Clippers team. This is obviously simplified, using just nine players, but should work to give us a rough estimate. Career minutes per game were used for each player when possible to project playing time, although they had to be adjusted in some cases to reflect the distribution of talent on the team. For adjusted plus-minus, I included each player's adjusted plus-minus from the previous 3 seasons, but weighted it towards the most recent season.


Baron Davis 35.5 mpg, +7.02
Cuttino Mobley 37.0 mpg, -1.42
Al Thornton 27.3 mpg, -4.43
Elton Brand 38.3 mpg, +5.91
Chris Kaman 29.1 mpg, -2.00

Tim Thomas 21.7 mpg, -0.33
Brevin Knight 16.3 mpg, +1.18
Quinton Ross 16.1 mpg, -2.33
Eric Gordon 18.7 mpg, -2.85

Adding up each player's scores and weighting for minutes played, the Clippers' 08-09 scoring margin (per 100 possessions) projects to be 3.45, which would make them about a 50 win team. Obviously, this would be a big year for the Clippers, although it would not make them a championship contender. Still, I estimate that the addition of Davis and the return of a healthy Brand should add about 9.9 points to the team's scoring margin, turning them from one of the weaker teams in the league into a legitimate playoff team.

There is of course uncertainty in this estimate. Baron Davis may not post the same high rating for a new team. Elton Brand may not be as good as he was before his injury. The estimates for Al Thornton and Eric Gordon are pretty much a shot in the dark. I gave Gordon the average rookie rating for the 2007 draft class of -2.85. Thornton's rating as a rookie was -5.57 but I adjusted it slightly upwards to account for second-year improvement. Still, without extensive study, it is hard to know how to expect Thornton's rating to change in year two. If he were to become even a league-average player, it could propel the Clippers to 55 wins or more. And of course, the Clippers' roster may change. For one, I am assuming here that they don't resign Corey Maggette. Still, a 50 win projection seems like a decent ballpark estimate for a team led by two very strong players in Baron Davis and Elton Brand, and this is where this kind of analysis can come in handy.

As for the Warriors, I won't try to project their roster for next year, as it seems certain that they will try to retool through free agency, perhaps adding a point guard, or perhaps trading away veteran talent to begin rebuilding. That said, according to adjusted plus-minus, Baron Davis added about 5.1 points to the team's scoring margin in 2008, meaning that without him, they could expect to fall from 48 to about 37 wins. The playoff window seems to have passed for Golden State, and they will have to think hard about their moves going forward.