The job of a Major League Baseball player is to help his team win games, for the ultimate purpose of making the playoffs and winning the World Series. Since the early history of Major League Baseball, pitchers have been credited with Wins and Losses as official measures of the effectiveness of their pitching. Of course, Pitcher Wins are a fairly crude measure of how well a pitcher did his job, as wins are the product of the performance of the entire team - batters, baserunners, and fielders, in addition to pitchers. Nevertheless, the concept of measuring a player's exact contribution to his team's wins is a good one.
Using play-by-play data, I have constructed a set of Player won-lost records that attempt to quantify the precise extent to which individual players contribute directly to wins and losses in Major League Baseball on the baseball field.
An overview of the website can be found here. Links to more detailed explanations of Player won-lost records can be found here.
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