Baseball Player Won-Lost Records

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.

While the implementation of Pitcher Wins as a measure of pitcher effectiveness is less than ideal, nevertheless the concept is perfectly sound. The ultimate measure of a player’s contribution – be he a pitcher, a hitter, a baserunner, or a fielder – is in how much he contributes to his team's wins.

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 explanation of Player won-lost records can be found here.

I have published two books on Player won-lost records which can be found here. I also have a YouTube channel which can be found here.

Thank you for visiting the site and please come back often!

A note to past visitors to the site. I have changed my calculations for positional average and expected context on January 10, 2019. These changes are described here.

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note: Player Won-Lost records are estimated for all seasons from 1921 to 2018.

The information used here was obtained free of charge from and is copyrighted by Retrosheet. Interested parties may contact Retrosheet at "".
Baseball player won-lost records have been constructed by Tom Thress. Feel free to contact me by e-mail, follow me on Twitter, and/or subscribe to my YouTube channel.