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Rick Lucks breaks down how to use BABIP to identify potential pitching sleepers and busts as his series on making sabermetrics more accessible to fantasy baseball managers continues.
While FIP is a useful tool to predict a pitcher's future ERA performance, fantasy managers should remember that ERA, not FIP, is what matters in most formats. This means that 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!
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How to Interpret BABIP for Pitchers
When calculating BABIP for hitters, we assume a neutral defense because they figure to see a balance of poor and skilled defenders as they travel 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 makes it easier to look at the quality of a team's defense. OAA measures each player's defensive contributions using Catch Probability. If a batted ball is caught by a player, 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 also 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 the pitcher on the mound, removing the guesswork from the equation.
The overall OAA leader last season was Dansby Swanson, who tallied 20 OAA for the Cubs. The leader among outfielders was rookie Brenton Doyle for the Colorado Rockies. Defensive metrics are somewhat sticky, so the presence of premium fielders such as Swanson or Doyle can help pitchers sustainably outperform their FIP.
Merrill Kelly of the Arizona Diamondbacks led all pitchers in defensive support received in 2023 with 14 OAA behind him. Arizona ranked second in the MLB with 34 OAA as a team last year, so Kelly will probably receive above-average defensive support again in 2024. However, he probably won't get as much defensive support as last year. You may not want to bet on a repeat of last season's 3.29 ERA as a result.
Last year's example was Cal Quantrill, who saw his ERA balloon from 3.38 in 2022 to 5.24 last season. There were multiple reasons for this, but going from 15 OAA of support in 2022 to -4 in 2023 despite Cleveland's ranking as the eighth-best defensive club overall last season was a factor.
There are other defensive metrics, but they are much more abstract than OAA while also leaving out important pieces of the puzzle. 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.
For example, Jesus Luzardo led pitchers in DRS in 2023 with seven over 178 2/3 IP. Luzardo has always been an outstanding defensive pitcher, posting three DRS in 100 1/3 IP in 2022 and four in 95 1/3 IP in 2021. We can assume that Luzardo will continue to help himself with the glove.
However, remember that these stats are only somewhat sticky. Tyler Anderson led pitchers with five DRS in 2022 and posted three in 141 IP last year, but it wasn't enough to prevent his ERA from spiking to 5.43 in his first year as an Angel. 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 (.243 to .117 in 2023.) This stylistic difference also changes how much a given pitcher will benefit from (or be hindered by) a particular defender on his team. For instance, a groundball specialist would love to pitch in front of Swanson while a fly ball guy would benefit more from an elite outfielder like Doyle instead.
While the 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 .265 BABIP Justin Verlander allowed in 2023 was a fluke, and you would be partially right. However, Verlander combined a strong fly ball tendency (44.8 FB%) with an above-average IFFB% (16.5). The combination would be 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 puts a run on the board.
Sequencing luck is measured by strand rate or LOB%, and research shows that it is largely an unstable, luck-driven stat. In 2023, the league average LOB% was 71.9, 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, as a ground ball or fly ball specialist, may also impact his performance. If you would like to learn about other advanced stats, stay tuned to our series.
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