The WARP Rating System Explained

What is WARP? WARP stands for Wins Above Replacement Player. The term and concept are borrowed from sabermetrics and, specifically, Baseball Prospectus. Conceptually, the WARP system seeks to evaluate players in the context of a team made up of them and four completely average players. The performance of this team is then compared to that of a team made up of four average players and one replacement-level player. The method also draws heavily on the work of Dean Oliver. What are the benefits of this method? For one, this rating system is very flexible. Players can be rated on a per-minute basis (using the theoretical "winning percentage" of the team with four average players), in terms of their offense and defense and in terms of their overall value (WARP itself). Using replacement level shows the value of players who can play heavy minutes and avoid injury while continuing to perform above replacement level. Using wins gives a measure of value that is easy to understand and constant over time. Lastly, by eschewing the traditional linear weights method so common in basketball analysis, I believe WARP does a better job of incorporating defensive value. What are the limitations? Like all rating systems based on box-score data, WARP cannot account for contributions that are not tracked in the box score, most notably on defense. It does no better than linear weights methods at evaluating players like Bruce Bowen. Also, it requires a number of assumptions - the value of assists, the trade-off between usage and efficiency, and replacement level. WARP in 2007-08 TOP WARP TOP WIN% (>500 minutes) Player Tm Win% WARP Player Tm Win% WARP --------------------------- --------------------------- Paul NOH .805 24.4 Paul NOH .805 24.4 James CLE .781 23.0 James CLE .781 23.0 Howard ORL .714 19.1 Garnett BOS .749 16.1 Stoudemire PHX .730 17.5 Stoudemire PHX .730 17.5 Duncan SAN .727 17.2 Duncan SAN .727 17.2 Bryant LAL .671 17.0 Ginobili SAN .718 14.5 Garnett BOS .749 16.1 Howard ORL .714 19.1 Nowitzki DAL .678 15.1 Billups DET .702 15.0 Billups DET .702 15.0 Bynum LAL .698 5.9 Ginobili SAN .718 14.5 Nowitzki DAL .678 15.1 TOP OFFENSIVE RATING TOP DEFENSIVE RATING Player Tm ORtg Player Tm DRtg ----------------------- ----------------------- Paul NOK 115.1 Camby DEN 99.9 James CLE 113.1 Johnson DET 101.2 Nash PHX 112.4 Garnett BOS 101.3 Billups DET 112.1 Smith ATL 101.4 Ginobili SAS 111.2 Howard ORL 101.4 Stoudemire PHX 111.1 Marion PHX 101.5 Calderon TOR 111.1 Duncan SAS 101.5 Williams UTA 110.9 Kaman LAC 101.7 Landry HOU 110.7 Wallace DET 101.9 Powe BOS 110.5 Wallace CHI 102.1