What infield OAA tells us about shortstops?

As I have stated previously the Infield Outs Above Average (OAA) metrics available on Baseball Savant contains a plethora of information. You can look at individuals and not only see their overall defensive value but you can breakdown the individuals plays via the probability of success, exit velocity, handedness of batter and quite a few others.

In this piece we are going to take a deeper dive into how shortstops accrue their OAA by looking at the 5 best and 5 worst shortstops by OAA in 2019.

The Best

As you may already know Javier Baez had the highest OAA with 19, let’s look at how he has gotten those outs. The graph below shows the number of plays by estimated success rate, 5% buckets, as well as the Cumulative OAA for Javier Baez in 2019.  (For the rest of this piece columns which say 5% mean plays which fell in the 0-5% success rate range. So, ones which say 100% mean 95-100%.)

Here we can see that the vast majority of plays which Baez faced were on the easier side and we can also see that is where he made his biggest OAA gains. He didn’t make an out on a play which had less than 25% but once above that level he was consistently above average for all buckets bar one (85-90% bucket). Baez makes some great plays that we wouldn’t expect but also is fantastic at doing the simple plays well, even when out of the standard shortstop locations.

Baez distribution of chances is very much in line with the league distribution with most players seeing 80% of their plays being in the 80-100% estimated success rate range. If we compare Baez’s cumulative OAA to the others in the top 5 you will see that there are two types of top shortstop.

Like Baez, Trevor Story and Andrelton Simmons pick up significant OAA on plays with success rate lower than 85% whilst Nick Ahmed and Paul DeJong aren’t much above league average before that point. It is worth noting that this is a counting stat so those who have more game time will see more plays and therefore have more chance to gain or lose OAA. Simmons had on 300 plays in 2019 compared to DeJong’s 504.

But what they all do is excel at is completing the very probable plays and due to the volume of plays that occurring in these ranges, whilst them not all being 99%+ plays, they make huge gains in OAA.

Nick Ahmed won’t have anywhere near the same highlight reel that Javier Baez does in 2019, but he is the best at not making simple mistakes and this brings his value almost in line with with Baez. Ahmed had 382 plays with an estimated success rate of 85% or higher, he was successful on all bar 9 of these plays (a 98% success rate). That rate is the best of any shortstop, Ahmed makes playing shortstop look easy.

It is very interesting that most of the overall OAA for these top players has come from converting the easiest chances, if we would compare that to the oufilders with the most outfield OAA you will see a large difference. For the top outfields 75-85% of their OAA comes from plays which have a success rate of 0-90% but for these top 5 shortstops it ranges from 30-65% of their OAA comes from these plays. With Ahmed and DeJong on the low end and Simmons and Story on the high end.

The Worst

We have looked at the best, now how about the worst. I took the worst 5 players who were primarily shortstops in 2019.

As you can see these 5 were all above or around average cumulatively for plays up 70% estimated success, if you compare these 5 to Nick Ahmed they were better than him on plays below 50%. But where they falter is in the exact places the top 5 thrive, putting away the easy chances. For most of them this comes down to throwing errors.

MLB did a piece on what is happening with Tatis Jr. so I won’t go into detail on him but it was throwing errors. These 3 examples of throwing errors from Polanco are part of 13 errors on plays that his OAA is calculated from. He would still be a below average shortstop without them going from -16 to -4 but given the top 5 players average 3.6 errors (18 in total) we shouldn’t expect him to achieve zero errors. So, he could get to roughly -7 OAA just by removing most of these throwing errors.

Also, one OAA equals roughly 0.75 runs, those 13 errors cost Polanco and the Twins around 1 WAR over the 2019 season. Defensively, by OAA alone, the difference between Polanco and Baez was about 2.5 wins in 2019.

Newman, Martin and Rosario all had at least 7 errors on plays counting for OAA. Newman & Martin with some very poor throwing errors in there. Rosario on the other hand had quite a few fielding errors.

For bad shortstops 60% of their negative OAA comes from plays of 0-90% estimated success and for comparisons bad outfielders get 75% of their negative OAA comes from plays of 0-90%. 

This data set will continue to grow and develop with new iterations. Tom Tango has stated that in the future they plan to show the data split out by the three main components of infield OAA. Reaching the ball, fielding the ball and the throw subsequently beating the man. When this data comes out it will be interesting to see where these players show differences, I would expect Polanco to look poor on the throwing part and Rosario to look poor on the fielding part.

At MLB level the difference between being a great shortstop and a poor one is getting the fundamentals right on the ‘easier’ plays. This should be shown to all young baseball players, being the best shortstop it isn’t about being flashy in defence it is about making it look boring.

All videos are the copyright of MLB and are obtained through Baseball Savant.


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