Outs Above Average

Mike Petriello at mlb.com has a story about the new fielding metric called "Outs Above Average" or OAA. He links to a much more detailed background piece by Tom Tango on the MLB Tech blog. Both are long but are worth a look--there is a whole new world out there because of Statcast and we have to start learning about it. I should note that the articles are particular to the infield component of OAA, the outfield stuff is handled differently.

Since all batted balls are tracked (via radar) and the movements of all the players tracked as well (via stereo camera systems) the combination of the two technologies allows for the measurement of speed, direction, distance, and more on every play. Nowadays the "eye test" is not simply something a fan can do from his or her seat (at the game or in front of the TV) but an actual data record that can be revisited at MLB's clearinghouse site for Statcast data, Baseball Savant.

Fielding is a tough nut to crack and it is especially tough in this era because of infield shifts. Something like one-third of all pitches last season involved at least one shifted infielder! DRS and UZR have become part of the new saber-landscape but they will likely be supplanted by OAA simply because it is built on some of the things that the earlier stats relied on and is enhanced with real-game information. Not only that, it is a computer model which of course can be refined as new data come in and new problems with measurement and evaluation get solved (or at least improved upon).

The argument for OAA is that it is intuitive. We, as fans, naturally "compute the odds" as we watch a play unfold. We see the shortstop chase down a ball in the hole and think about the runner heading to first and "calculate" the probability that the throw will get there before him. When the runner is safe we wonder if perhaps the runner was faster than we expected, the fielder had a hitch in his throw, the ball was further into the outfield grass than we thought, etc. We've seen many many such plays and have a sense of what should work and when and thus we can be surprised by an unusually strong throw or quick feet by the fielder or dismayed by a failure to get what should have been an out.

OAA determines the likelihood of success for the fielder depending on how far he has to go to get the ball, how fast the ball was hit, and how quickly the runner gets down the line. Good fielders convert more "unlikely" chances and make the "routine" plays a higher percentage of the time. Like I said we do this in our heads anyway, without actual numbers but with a large history of observations. Would it surprise you that Javier Baez, Nolan Arenado, and Andrelton Simmons rate the best on this metric? Right now OAA can't include everything (like double plays, pitcher failing to cover a base, etc.) but it's a good start. I think we might have a real defensive stat emerging that we can rely on.

--M.C.


p.s. Do you want to know how Giants infielders were ranked in 2019? Go to the Statcast leaderboards and select Infield Outs Above Average from the pull-down menu and you'll find out. (Brandon Belt was 61st overall and 8th among first basemen, and Evan Longoria was 55th overall and 11th among third baseman, for example. Sadly, Brandon Crawford was 189th overall and 27th among shortstops. That seems to fit with what we watched. Every player has a specific profile that provides more granular information. Warning: major time sink!)