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Welcome RotoBallers to our overview of BABIP (for pitchers). This article is a deeper dive into pitcher BABIP, and is part of our ongoing series "Using Sabermetrics for Fantasy Baseball."
In this article, we'll explain what pitchers can do to control their BABIP and explore how a club's defenders may influence BABIPs allowed using easily understandable terminology.
You can find our entire sabermetrics glossary, which includes links to many other sabermetric stats as part of this series. Each stat deep dive will be released over the next few days. Stay tuned!
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What Is BABIP (for Pitchers)? Sabermetrics Glossary
While FIP is a useful tool to predict a pitcher's future ERA performance, fantasy managers should remember that ERA, not FIP, matters in most formats. We are interested in the "luck" that separates the two statistics.
While some of this luck is unpredictable, we can and should predict some of what goes into a pitcher's bottom line. BABIP plays a big role in the variation of a pitcher's perceived luck, but it may not be as clear-cut as it seems.
A pitcher's BABIP appears on FanGraphs's first graph of their player page, so it's easy to locate. Let's get to it!
How to Interpret BABIP for Pitchers
When calculating BABIP for hitters, we assume a neutral defense because they figure to see a balance of defenders around the league. This is not true for pitchers, who always pitch in front of their club's defenders.
Outs Above Average (OAA) is a Statcast metric that measures the quality of a team's defense. OAA measures each player's defensive contributions using Catch Probability. If a batted ball is caught, the player receives OAA credit equal to 1 -- the ball's Catch Probability. For example, a successful catch on a ball with a 40% Catch Probability is worth 0.6 OAA (1 - 0.4 = 0.6).
Players lose points equal to the batted ball's Catch Probability if they flub the catch. Missing the ball in the example above would subtract 0.4 from the player's OAA. One of the best features of OAA is that you can sort the leaderboard by team and even pitcher, removing guesswork from the equation.
The overall OAA leader last season was Andres Gimenez, who tallied 21 OAA for the Guardians. The leader among outfielders was Jacob Young for the Nationals at 20 OAA. Defensive metrics are somewhat sticky, so premium fielders like Gimenez or Young can help pitchers sustainably outperform their FIP.
Colin Rea of the Brewers led all pitchers in defensive support received in 2024 with 11 OAA behind him. Milwaukee ranked third in MLB with 31 OAA as a team last year, so their pitchers will probably receive above-average defensive support again in 2025. However, Rea is a Cub now. We wouldn't expect him to receive the same level of defensive support even if he didn't switch teams.
Last year's example was Merrill Kelly of the Diamondbacks, who saw his ERA balloon from 3.29 in 2023 to 4.03 last season. There were multiple reasons for this, but going from 14 OAA in 2023 to two in 2024 was a factor.
There are other defensive metrics, but they are much more abstract than OAA while ignoring key details. Ultimate Zone Rating (or UZR) makes no effort to account for shifting, rendering it completely obsolete in this author's estimation. Defensive Runs Saved (DRS) has one fantasy purpose: measuring the value of a pitcher's defensive contributions to his cause.
Tanner Bibee and Jake Irvin tied for the lead in DRS last year with six. Bibee is much more interesting in fantasy, so let's focus on him. His 3.37 ERA was a little better than his 3.78 xERA or 3.72 xFIP, but he could sustain it if he helped himself with his glove. Unfortunately, Bibee only had one DRS in his rookie campaign, so he lacks history as a great glove.
Remember that these stats are only somewhat sticky. Tyler Anderson led pitchers with five DRS in 2022 and posted three in 141 IP in 2023, but it wasn't enough to prevent his ERA from spiking to 5.43 in his first year as an Angel. Anderson dropped to -1 DRS last season, but his 3.81 ERA was better than his 4.37 xERA or 4.85 xFIP.
Draft pitchers for their pitching skills, not because they can field their position.
What Else Impacts a Pitcher's ERA?
BABIP is also partially determined by a pitcher's style. An extreme groundball pitcher may have a higher BABIP because grounders have higher BABIPs than fly balls (.245 to .110 in 2024).
This stylistic difference also changes how much a given pitcher will benefit from a particular defender on his team. For instance, a groundball specialist would love to pitch in front of Gimenez while a flyball guy would benefit more from an elite outfielder like Young instead.
While defense is largely out of a pitcher's control, some pitchers can control their BABIP to a degree. For example, you would probably be tempted to say that the .247 BABIP Bailey Ober allowed in 2024 was a fluke, and you would be partially right.
However, Ober combined a strong fly ball tendency (50.3 percent FB%) with a solid IFFB% (10.3 percent). The combination is expected to produce a low BABIP allowed.
Every pitcher allows a few hits, and the sequencing of these events may also cause a difference between a pitcher's FIP and ERA. Allowing three base hits over three innings is probably harmless while allowing three hits in one inning and then nothing in the next two frames likely breaks the shutout.
Sequencing luck is measured by strand rate or LOB%, and research shows that it is largely an unstable, luck-driven stat. In 2024, the league average LOB% was 72.1 percent, with higher numbers generally forecasting a higher ERA moving forward. Elite strikeout guys tend to be the best at getting the K "when they need it," and as such may sustain slightly elevated strand rates.
Conclusion
To conclude, a pitcher's BABIP includes some unknown variables but also some predictable inputs. The quality of his defense can help or hurt him. Sequencing does not affect BABIP but can impact a pitcher's ERA substantially. A given pitcher's style may also impact his performance.
