Pitcher BABIP: Using Sabermetrics for Fantasy Baseball

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 the first graph of their player page on FanGraphs, 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, as they always pitch in front of their own club's defenders. A team with Kansas City's Nicky Lopez and his 25 Outs Above Average in 2021 figures to provide better defense to its pitchers than a team that lacks a premium fielder, helping pitchers sustainably outperform their FIP.

Outs Above Average is a Statcast metric that makes it easier to look at the quality of a team's defense. Outs Above Average, or 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.

For example, the St. Louis Cardinals led baseball with 47 OAA last season and Adam Wainwright was on the mound for 25 of them. The Cards are likely to field a strong defensive club again in 2022, but expecting one pitcher to again benefit from more than half of their total OAA would be unwise. Framber Valdez of Houston received the second-most OAA with nine. As such, Wainwright should be projected to pitch in front of a strong defense but not to the same extent that he did last year.

Lopez led all infielders in OAA last season, while Tampa's Manuel Margot took the top spot among outfielders with 16. 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 the shifts in today's game, 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 own cause.

For example, Dallas Keuchel led pitchers in DRS in 2021 with 12 over 162 IP. Max Fried took second place with just six over a comparable workload. This is nothing new for Keuchel, who has over 60 DRS over his career. Fantasy managers have known for years that Keuchel posts lower than average BABIPs when he's on despite being a ground ball pitcher, but the reason isn't some magical contact suppression ability. It's the fact that Keuchel rates as roughly double the defender of any position player if you prorate his seasonal DRS over a position player's number of innings.

He helps himself with a repeatable skill, but his actual pitching was subpar last year with a 5.28 ERA. Statcast says that he deserved an ERA of 6.20 based on the batted balls he allowed and a complete lack of strikeout stuff, so his glove shaved a run off his ERA. You still shouldn't draft him this year.

What else impacts a pitcher's ERA?

BABIP is also partially determined by a pitcher's style. An extreme ground ball pitcher may have a higher BABIP against because grounders have higher BABIPs than fly balls (.236 to .115 in 2021.) 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 ground ball specialist would love to pitch in front of Lopez while a fly ball guy would benefit more from an elite outfielder like Margot 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 Max Scherzer allowed in 2021 was a fluke, and you would be partially right. However, Scherzer combined a strong fly ball tendency (48.3 FB%) with an above-average IFFB% (9.7%). 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 2021, the league average LOB% was 72.1%, 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 more about other advanced stats, stay tuned.

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