Plus Minus

Plus/Minus is the fielding metric developed by John Dewan and introduced to the public in his book The Fielding Bible in February of 2006.

In the book, Dewan goes into great length describing the new fielding system. Video Scouts at Dewan's company, Baseball Info Solutions (BIS), review video of every play of every major league game and record detailed information on each play, such as the location of each batted ball, the speed, the type of hit, etc. Using this in-depth data, he determines how each player compares to his peers at his position.

A player gets credit (a "plus" number) if he makes a play that at least one other player at his position missed during the season, and he loses credit (a "minus" number) if he misses a play that at least one player made. The size of the credit is directly related to how often players make the play. Each play is looked at individually, and a score is given for each play. Sum up all the plays for each player at his position and you get his total plus/minus for the season. A total plus/minus score near zero means the player is average. A score above zero is above average and a negative score is below average. Adam Everett turned in a +43 at shortstop in 2006, one of the best seasons on record. That means he made 43 more plays than the average MLB shortstop would make.

For corner infielders and outfielders, an additional adjustment is made to take into account balls that go for extra bases. This adjustment was coined "Enhanced Plus Minus". Plus/Minus numbers for these positions are in terms of "bases" rather than "plays". An Enhanced Plus/Minus score of +15 in the centerfield, for example, represents 15 bases saved above the average player at the position.