Outs Above Average (OAA) is a range-based metric of skill that shows how many outs a player has saved. Prior to 2020, OAA was an outfield-only metric. But it has been expanded to include infielders. OAA is calculated differently for outfielders and infielders (details below).
Outs Above Average for outfielders starts with Catch Probability, which takes the distance an outfielder must go, the time he has to get there, and the direction he travels to put a percentage of catch likelihood on each individual batted ball. OAA for outfielders is the season-long cumulative expression of each individual Catch Probability play. For example, if an outfielder has a ball hit to him with a 75 percent Catch Probability -- that is, one an average outfielder would make three-quarters of the time -- and he catches it, he'll receive a +.25 credit. If he misses it, he'll receive -.75, reflecting the likelihood of that ball being caught by other outfielders.
Adding up credit for every play made or not made contributes to a seasonal Outs Above Average number. In 2019, Victor Robles led MLB outfielders with +23 OAA.
In addition, the leaderboards show columns for "Expected Catch Percentage," "Actual Catch Percentage," and "Catch Percentage Added," providing the ability to see how a player has performed on a rate basis.
• Expected Catch Percentage shows how many plays an average outfielder would be expected to come up with based on the difficulty of the batted balls hit to the outfielder in question. Of the outfielders with at least 150 chances in 2017, Mike Trout's Expected Catch Percentage of 89 was the highest, meaning an average outfielder catches 89 percent of the balls Trout saw. This shows he got the least challenging opportunities sent his way, while Norichika Aoki, at 77 percent, got the toughest.
• Actual Catch Percentage shows the production of the actual fielder on the balls hit his way. Given the difficulty of batted balls, Trout would be expected to make the catch 89 percent of the time, but in actuality, he made the catch 88 percent of the time.
• Catch Percentage Added shows the difference between the Expected and Actual numbers. For example, Heyward and Ben Gamel were each given the same difficulty of opportunities, being expected to catch 86 percent. But with an Actual Catch Percentage of 90, Heyward added four points of value. Meanwhile, Gamel's Actual Catch Percentage was 83, so he subtracted three points of value. Heyward was seven points more valuable on a rate basis than Gamel, and +18 (comparing his +10 to Gamel's -8) Outs Above Average on a cumulative basis.
Outs Above Average for infielders takes the following factors into account.
• How far the fielder has to go to reach the ball ("the intercept point").
• How much time he has to get there.
• How far he then is from the base the runner is heading to.
• On force plays, how fast the batter is, on average. (A runner's average Sprint Speed is used in the calculation, rather than his Sprint Speed on that particular play. For new players with no data, a league-average -- 27 ft/sec -- score is used; once the player qualifies for the leaderboard, all of his previous plays are re-run.)
The Statcast technology allows us to know exactly where each fielder stands, which is helpful in a baseball world where shifting and out-of-position defenders are commonplace. What that means is that every tracked play is accounted for, regardless of if the third baseman is standing in his regular spot, at shortstop or in short right field. It allows you to know exactly "how far" and "how much time," regardless of shifts. It also allows for an OAA breakdown by fielder role.
For example, Nolan Arenado was +17 OAA in 2019, all coming as a third baseman, because he played every single inning of his season at third base. But that doesn't mean he was always standing at third base. Due to shifting, Arenado's +17 actually breaks down into +14 OAA where third basemen typically play, and +3 OAA where shortstops play.
Javier Baez led all infielders with +19 OAA in 2019. His breakdown: +17 where shortstops typically play, and +2 where second basemen play, even though he technically was never listed on the lineup card as a second baseman in 2019.