The new kid on the block, OAA-infield
OAA-infield works like OOA-outfield; analysis of past StatCast data created a library used to determine what constitutes an average play for infielders, based on where the infielder started, which way and how far he went to make the play.
"(thus) making it a range-based metric of fielding skill that accounts for the number of plays made and the difficulty of them"
Statheads will enjoy the granularity OOA-infield provides, while casual fans may misunderstand what the granularity means. OAA-I measures the player’s ability to go to their left, right, front, and back as well as how they handle balls hit by left-handed and right-handed batters.
Petriello provided a guide for OAA-infield, like the one he provided for the outfield, which provides further details about the metric’s design.
"• 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, and • 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.)"
OAA is role-specific, rather than position-specific; it doesn’t matter whether the third baseman makes the play near third-base or playing in the shortstop position, his OOA depends on which way he had to move to get the ball.
Roles and qualified players
OAA-I defines infield roles for each infield position, as shown in this table.
1B2BSS3BClose to line
Behind first
Up the middle
Close to line
Straight Up
Towards 3.5 hole
Towards second
Straight Up
Towards 3.5 hole
Straight Up
Straight Up
Towards 5.5 hole
Towards second
Towards 5.5 hole
Up the middle
Statcast records precisely where the fielder stood before the play, eliminating the positioning argument, at least in theory. Based on the player’s position when the batter hits the ball, the OAA algorithm assigns a role to the fielder. This example comes from the Petriello post.
". . . 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 . . . Due to shifting, Arenado’s +17 actually breaks down into +14 OAA where third basemen typically play, and +3 OAA where shortstops play."
More on that later.
You hear the term qualified when discussing awards like Rookie of the Year or Cy Young Award, but OAA sets a different standard.
- A qualified outfielder or infielder, other than the first baseman, must have one fielding attempt per team game played.
- A qualified first baseman must have one fielding attempt per every other team game played.