Back to Basics: What is Outs Above Average?

Outs Above Average (OAA) is a defensive statistic that measures fielding skill. It represents the amount of outs a player has saved. It’s calculated by assigning values to plays based on their difficulty, and then adding the values of each play for a season-long cumulative number. OAA is becoming a more popular (and easy to understand!) stat when talking about a player’s defense. It is calculated differently for outfielders and infielders (both discussed below).

What is a good OAA value?

Zero is an average number of outs expected for an average fielder. Anything greater than zero indicates that a fielder is above average skill level and makes plays that average fielders may not be able to. Anything less than zero indicates that a fielder may have a tendency to miss plays, even average ones from time to time.

So, the higher the better!

Outs Above Average for Outfielders  

Outs Above Average for outfielders is related to catch probability and considers:

• Distance traveled by the player to get to the ball
• Direction traveled by the player
• Time for the player to get to the ball
• Proximity to the wall

The catch probability is determined based on the above three factors. Tougher plays have lower catch probability. If the catch is made, the player receives positive credit towards his Outs Above Average number. If the catch is not made, he receives negative credits.

Example: If a ball is hit to an outfielder with the catch probability of 75%, it means there is a 75% chance an average outfielder catches the ball.  If the player makes the catch, his OAA increases by +0.25. If he misses, his OAA is reduced by -0.75.

Here are the 2019 outfield leaders and their OAA:

• Victor Robles: 23
• Kevin Kiermaier: 17
• Lorenzo Cain: 14
• Harrison Bader: 13
• Delino DeShields: 12
• Byron Buxton: 12
• Manuel Margot: 11
• Mallex Smith: 10
• Mike Tauchman: 9
• Keon Broxton: 9

Back to Basics: Outfield Outs Above Average

So, what does all that really mean?

If we take a step back and really think about what this stat is measuring, it becomes even simpler. When you are watching a game and a ball is put in play, most of the time you should be able to tell whether that ball is going to fall for a hit or end as an out.

Depending on how big of a baseball fan you are, you can probably even estimate the chances that a ball is caught. For example, the chances that a routine flyball to the centerfielder is caught are very high, probably more than 95% of the time.

How do we know that? Firstly, the ball is a flyball, so we know it was hit pretty high up and will allow the fielder enough time to get to a good position to catch it. Secondly, the ball was hit to a location with easy access for the fielder (meaning he did not have to dive or put in that much extra effort to make this play). Thirdly, he is most likely running forward to make the catch or taking a few steps back (a difficult route to the ball is not required).  

So in the few seconds that this play takes place, you basically already calculated an out probability in your head. And that’s the same thing that OAA does (just with actual numbers!).

A Little More Complicated…

Getting into the details of OAA, balls in play are either automatic outs, automatic hits, or in between (known as the “opportunity space” for players). There is only a small percentage of balls that can go either way (hit or out), and this is where the best defenders stand out. This is also what OAA tries to highlight by assigning point values to plays.

Take a look at this graph for Gold Glove winner Kevin Kiermaier (Tampa Bay Rays CF). It shows all of the balls hit to him in 2019 and their results. For simplicity focus on the red dots (outs) and gray dots (hits).

The y axis of this graph is showing the hang time (time the ball is in the air), and the x axis is showing the distance Kiermaier was from where the ball landed. The lower right corner of the graph is where the ball was in the air for a short amount of time, and Kiermaier was a long distance from it. When balls were hit under these conditions, they fell for hits. The upper left corner of the graph is where the ball was in the air for a long time, and Kiermaier was a short distance from it. When balls were hit under these conditions, they were caught.

The teal diagonal space running through the middle of the graph is the opportunity space. Based on average, this space is where balls can either fall for a hit or be caught. Great defenders will have more red circles in this area (outs) then gray circles (hits). As you can see in the graph, most of the balls hit under these conditions were caught for outs by Kiermaier. The ones he missed were the ones very closed to the line before entering the automatic hits zone.

Not to further complicate this, but catch probability also considers player route and proximity to the wall. When a player has to run back, the catch probability is decreased (since it is a harder play). The same applies to if the player is close to a wall. When a player has to run back and is close to a wall, the catch probability decreases even further.

Outs Above Average for Infielders

Outs Above Average for infielders considers:

• Distance traveled by the player to get to the ball, also known as the “intercept point”
• Time for the player to get to the ball
• Distance from the player to the base that the runner is heading to
• Runner’s sprint speed (on force plays only)

When the runner’s sprint speed is not known, league average is used (27 ft/sec) until their spring speed is determined. This is typically the case for new players.

The technology used to determine this metric (Statcast) is able to identify exactly where the fielders are positioned in order to calculate a more accurate result. Shifts or fielders playing different positions will not have a negative effect on the determination of their OAA. Every ball hit to that player, regardless of where he is positioned, will be considered in the statistic.

Here are the 2019 infield leaders and their OAA:

• Javier Baez:19
• Nolan Arenado: 17
• Andrelton Simmons: 16
• Nick Ahmed: 16
• Trevor Story: 15
• Matt Chapman: 14
• Paul DeJong: 13
• Matt Olsen: 12
• Jose Iglesias: 12
• Freddy Galvis: 12

Back to Basics: Infield Outs Above Average

If a ground ball is hit hard right to your shortstop, it is safe to assume he will be able to throw the ball to first for the out. If it’s a slow roller or he has to run to it, the chances he makes the play at first start to go down.

So what is actually being considered when determining OAA for infielders?

First thing: What is the probability that the player reaches the ball (the intercept point)? If the ball is hit hard and rolls several feet away from him, there is a good chance it might end up in the outfield. If it’s a slow roller right toward him, chances are he gets to it in time.

Second: How long does the player takes to reach the ball? The faster he gets there, the more likely a play is made.

Third: How fast is the batter? When the fielder arrives at the intercept point, the batter is already on his way to first. If the batter is really fast, the play becomes a lot harder to make.

Fourth: How much longer it will take for the batter to make it to first? Depending on how fast he is, the batter has already made progress on his path to first.

 Fifth: How far away is the fielder is from the bag? Can he make the throw in time? It is harder to get an out for a third basemen than a second baseman because of the extra distance the ball needs to travel.

If you have any questions or want to learn more about OAA let me know!

And here is a really good reference for some more information about how this stat is calculated