OAA measures fielding skill by measuring outs above average. Saved outs are represented by this number. For a season-long cumulative number, plays are assigned values based on their difficulty, and the values are added together for each play.

Increasingly, OAA is used when thinking about a player’s defense (and it’s easy to understand!). Outfielders and infielders are calculated differently.

A fielder who outs above average zero outs has an expected number of outs of zero. If the fielder’s skill level exceeds zero, he or she may make plays that average fielders cannot. The fielder may miss average plays from time to time if the percentage is below zero.