Win Probability Added
Encyclopedia
Win probability added is a sport statistic which attempts to measure a player's contribution to a win by figuring the factor by which each specific play made by that player has altered the outcome of a game. It is used for baseball
and American football
.
, however, win probability added has become substantially easier to calculate. The win probability for a specific situation in baseball (including the inning, number of outs, men on base, and score) is obtained by first finding all the teams that have encountered this situation. Then the winning percentage of these teams in these situations is found. This probability figure is then adjusted for home-field advantage. Thus win probability added is the difference between the win probability when the player came to bat and the win probability when the play ended.
, since both are baseball statistics that attempt to measure a player's win contribution. However, they are quite different. In win shares
, a player with 0 win shares
has contributed nothing to his team; in win probability added, a player with 0 win probability added points is average. Also, win shares
would give the same amount of credit to a player if he hit a lead-off solo home run as if he hit a walk-off solo home run; WPA, however, would give vastly more credit to the player who hit the walk-off homer.
, St. Louis Cardinals' third-baseman David Freese
posted the best WPA in Major League Baseball postseason history, with a 0.969, which was 0.099 better than the now-second-best WPA of .870, posted by the Los Angeles Dodgers' Kirk Gibson
in Game 1 of the 1988 World Series
. The third- and fourth-best WPAs are .854 (by the San Diego Padres' Steve Garvey
in Game 4 of the 1984 National League Championship Series
) and 0.832 (by the the Cardinals' Lance Berkman
in Game 6 of the 2011 World Series).
Baseball
Baseball is a bat-and-ball sport played between two teams of nine players each. The aim is to score runs by hitting a thrown ball with a bat and touching a series of four bases arranged at the corners of a ninety-foot diamond...
and American football
American football
American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team's end zone. Known in the United States simply as football, it may also be referred to informally as gridiron football. The ball can be advanced by...
.
Explanation
Some form of win probability has been around for about 40 years; however, until computer use became widespread, win probability added was often difficult to derive, or imprecise. With the aid of RetrosheetRetrosheet
Retrosheet is a non-profit organization whose website features major league baseball box scores and play-by-play narratives for almost every contest from 1871–1872, 1874, 1911 NL, and 1918–2010...
, however, win probability added has become substantially easier to calculate. The win probability for a specific situation in baseball (including the inning, number of outs, men on base, and score) is obtained by first finding all the teams that have encountered this situation. Then the winning percentage of these teams in these situations is found. This probability figure is then adjusted for home-field advantage. Thus win probability added is the difference between the win probability when the player came to bat and the win probability when the play ended.
Win probability and win shares
Some people confuse win probability added with win sharesWin Shares
Win shares is the name of the metric Bill James describes in his 2002 book Win Shares.It considers statistics for baseball and basketball players, in the context of their team and in a sabermetric way, and assigns a single number to each player for his contributions for the year. A win share...
, since both are baseball statistics that attempt to measure a player's win contribution. However, they are quite different. In win shares
Win Shares
Win shares is the name of the metric Bill James describes in his 2002 book Win Shares.It considers statistics for baseball and basketball players, in the context of their team and in a sabermetric way, and assigns a single number to each player for his contributions for the year. A win share...
, a player with 0 win shares
Win Shares
Win shares is the name of the metric Bill James describes in his 2002 book Win Shares.It considers statistics for baseball and basketball players, in the context of their team and in a sabermetric way, and assigns a single number to each player for his contributions for the year. A win share...
has contributed nothing to his team; in win probability added, a player with 0 win probability added points is average. Also, win shares
Win Shares
Win shares is the name of the metric Bill James describes in his 2002 book Win Shares.It considers statistics for baseball and basketball players, in the context of their team and in a sabermetric way, and assigns a single number to each player for his contributions for the year. A win share...
would give the same amount of credit to a player if he hit a lead-off solo home run as if he hit a walk-off solo home run; WPA, however, would give vastly more credit to the player who hit the walk-off homer.
MLB postseason
In Game 6 of the 2011 World Series2011 World Series
The 2011 World Series was the 107th edition of Major League Baseball's championship series. The best-of-seven playoff was played between the American League champion Texas Rangers and the National League champion St...
, St. Louis Cardinals' third-baseman David Freese
David Freese
David Richard Freese is a third baseman for the St. Louis Cardinals of Major League Baseball. A star high school player, Freese chose not to play college baseball in his freshman year of college, but returned to the game a year later...
posted the best WPA in Major League Baseball postseason history, with a 0.969, which was 0.099 better than the now-second-best WPA of .870, posted by the Los Angeles Dodgers' Kirk Gibson
Kirk Gibson
Kirk Harold Gibson is a former Major League Baseball player and currently the manager of the Arizona Diamondbacks. As a player, Gibson was an outfielder who batted and threw left-handed...
in Game 1 of the 1988 World Series
1988 World Series
-Game 1:Saturday, October 15, 1988 at Dodger Stadium in Los Angeles, CaliforniaBecause of using ace Orel Hershiser in Game 7 of the NLCS, the Dodgers had to open with rookie Tim Belcher in Game 1. Meanwhile, Oakland sent a well-rested Dave Stewart to the mound. Both pitchers, however, would have...
. The third- and fourth-best WPAs are .854 (by the San Diego Padres' Steve Garvey
Steve Garvey
Steven Patrick Garvey , nicknamed "Mr. Clean" because of the squeaky clean image he held throughout his career in baseball, is a former Major League Baseball first baseman and current Southern California businessman...
in Game 4 of the 1984 National League Championship Series
1984 National League Championship Series
-Game 1:Tuesday, October 2, 1984 at Wrigley Field in Chicago, IllinoisBob Dernier led off the game for the Cubs with a homer, and things went steadily downhill for the Padres as Chicago romped to a crushing 13–0 win in their first postseason game since 1945. Gary Matthews also homered in the first...
) and 0.832 (by the the Cardinals' Lance Berkman
Lance Berkman
William Lance Berkman is an American professional baseball outfielder and right fielder with the St. Louis Cardinals of Major League Baseball....
in Game 6 of the 2011 World Series).