Baseball has no shortage of advanced stats, and defensive metrics are some of the most important to understand. Whether you’re comparing Defensive Runs Saved (DRS), Ultimate Zone Rating (UZR), or Outs Above Average (OAA), knowing how they work and how they differ helps you appreciate elite defenders.
In this guide, you’ll learn:
- What each defensive metric measures
- How DRS, UZR, and OAA are calculated
- Which metric is most reliable
- Why some positions naturally have lower or higher scores
- How DRS, UZR, and OAA compare side by side
Let’s break down these stats step by step.
Our articles will frequently reference non-traditional baseball statistics when discussing the performance of our beloved Atlanta Braves.
Table of Contents
These stats get thrown around a lot and are not always explained. Does “defensive runs saved” mean a player saved that exact amount of runs with his defense? No. Does a lower DRS mean a player is worse than another? Not necessarily.
In order to ensure you are following along, we created a resource guide for commonly used stats, so you can put a face to the name.
What Is Defensive Runs Saved (DRS)?
Defensive runs saved is a metric that attempts to decide how many runs a player is better or worse than the average Major Leaguer at his position.
For example, if a player has three defensive runs saved at centerfield, that doesn’t mean he’s only saved three runs; it means he’s three runs better than the average MLB centerfielder. Three runs better is good when you consider that Major League caliber centerfielders are some of the best defensive players in the universe.
Why Do Great Center Fielders Have Lower DRS Scores?
Some positions, like shortstop and centerfield, have the best athletes and defensive players. Hence, the distance between the top player and the average player is not as significant a gap as at other positions like right field. The bar is higher at shortstop and centerfield.
How Is DRS Calculated?
DRS compares every play a fielder makes to the expected likelihood of that play being made. Plays with low probabilities get higher credit when made, and higher penalties when missed. These credits and debits are converted into “runs saved” or allowed over the season.
How Does DRS Scoring for Individual Plays Work?
If a fielder makes a play that is only made 10% of the time, he gets 0.9 points (1 minus 0.1). If he misses a play that is made 95% of the time, he gets -0.95 credit. This is why solid outfielders can end up with abysmal range ratings or OAA scores. They cannot overcome a bad read or two if they don’t make the highly improbable plays.
DRS vs OAA: What’s the Difference?
Defensive Runs Saved (DRS) is a comprehensive stat that measures how many runs a player saves or costs his team compared to an average defender. It includes range, throwing arm, double-play ability, scooping bad throws, and other position-specific skills. Outs Above Average (OAA) mainly measures range by calculating how often a player catches balls compared to expectations based on distance, time, and direction. OAA does not factor in throwing arm or other defensive skills. For example, Ronald Acuña Jr. might have a below-average OAA because it only looks at catch probability, but his strong throwing arm adds value to his DRS by preventing runners from advancing. In short, DRS captures a more complete picture of defense, while OAA focuses only on range.
How does DRS differ from other defensive metrics?
Unlike simpler fielding stats, DRS uses detailed play-by-play data and run impact estimates, making it more comprehensive than traditional errors or fielding percentage.
What Does a Positive or Negative DRS Mean?
A positive DRS indicates the fielder saved runs above average, while a negative DRS means he allowed more runs than an average defender.
What creates separation is the ability to make the low-probability plays consistently.
If you would like to delve into the depths of the Fielding Bible’s calculations, you can do so here.
MLB.com has a nice explanation of the stat in its glossary.
DRS uses Baseball Info Solutions data to chart where each ball is hit. Say, for instance, a center fielder sprints to make a nice catch on a fly ball. Then, say data from BIS tells us that similar fly balls get caught 60 percent of the time. That center fielder gains, essentially, 0.4 bonus points for difficulty.
MLB.com Glossary
If he can’t make the play, he loses 0.6 points. At the end of the day, that player’s overall score gets adjusted to the league average — and then that score gets adjusted for how many runs the once-adjusted score is worth.
What is Ultimate Zone Rating (UZR)?
UZR or Ultimate Zone Rating is calculated and used by Fangraphs and is very similar to defensive runs saved. It takes into account factors such as range, arm strength, and errors made. UZR compares the number of plays a player makes to the expected number of plays produced at their position, factoring in the batted ball type, location, and velocity.
According to Fangraphs, UZR is defined as follows:
UZR (ultimate zone rating): The number of runs above or below average a fielder is in both range runs, outfield arm runs, double play runs, and error runs combined.
Fangraphs Glossary
What Is Fangraphs’ “Def” Stat?
“Def” combines a player’s fielding value with positional adjustments, letting you compare players across positions on the same scale. For example, a shortstop and a third baseman can be directly compared with “Def.”
We’ll use former Braves shortstop Dansby Swanson as an example.
Dansby Swanson had a fabulous 2022 campaign for the Atlanta Braves. He was great with the bat and with the glove. According to Fangraphs, Dansby had a +9 defensive runs saved at shortstop.
Again, this means he was worth nine runs saved more than the average major-league shortstop. Being an average major-league shortstop is actually really good, so being worth nine runs saved better than average is excellent!
Fangraphs has come up with a stat called “Def” that shows you how many runs better Dansby was than the average defensive player, regardless of position.
To show how positional adjustments work, let’s look at Dansby Swanson’s 2022 season.
| 2022 | DRS | Def |
| Dansby Swanson | 9 | 21.5 |
This example highlights how “Def” can value a shortstop higher than a third baseman, even if the raw Defensive Runs Saved total is lower.
In 2022, 15 of the top 20 players in Def scores were either SS, C, or CF, these are some of the most demanding defensive positions. Def is a great tool to compare those players to an average player in the league instead of just at their position, like DRS and UZR.
We’ll contrast Dansby’s numbers with the overall leader in defensive runs saved. Dansby only finished with 9 defensive runs saved, and Ke’Bryan Hayes finished with 24.
Does this mean Ke’Bryan Hayes was better than Dansby on the defensive side? No. Even though Hayes had 15 more DRS than Swanson, Dansby finished with a higher “Def” score than Hayes.
Hayes was an excellent defensive player, but the bar was much lower at third base than at shortstop. Hayes was just that much better than the average third baseman, which is a lot worse than the average shortstop.
What is Outs Above Average (OAA)?
This statistic strictly looks at a player’s success based on catch probability. It is a portion of the formulas used in UZR and DRS, but doesn’t include other factors. OAA categorizes opportunities to catch a ball by the probability of other players at the position making the catch based on the distance to the ball, the time it takes to land, and the direction the ball is hit. If a player misses a ball with a 99% catch probability, they get -.99 from their OAA total. If they catch a ball with a 99% catch probability, they get .01 added to the OAA total. Does this sound familiar? Outs Above Average has much of the same concepts used in UZR and DRS, except it solely focuses on a player’s ability to get to a ball. Below is MLB.com’s official explanation of Outs Above Average.
Catch Probability expresses the likelihood for a ball to be caught by an outfielder based on opportunity time, distance needed, and direction. “Opportunity time” starts when the ball is released by the pitcher, and “distance needed” is the shortest distance needed to make the catch. Learn more about how direction is accounted for here. Read more about the details of how Catch Probability works here.
MLB Statcast Catch Probability Page
Outs Above Average (OAA) is the cumulative effect of all individual Catch Probability plays a fielder has been credited or debited with, making it a range-based metric of fielding skill that accounts for the number of plays made and the difficulty of them. For example, a fielder who catches a 25% Catch Probability play gets +.75; one who fails to make the play gets -.25. Read more about how Outs Above Average works here.