Using Sabermetrics For Fantasy Baseball Part 8: BABIP For Pitchers

While FIP is a useful tool to predict a pitcher's future ERA performance, fantasy owners should remember that ERA, not FIP, is what really 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 using batted ball profiles for pitchers. Let's get to it!

Editor's note: Be sure to check out all our strategy articles on how to win your fantasy baseball leagues. Our Sabermetrics series - Part 1: BABIP for Hitters, Part 2: HR/FB%, Part 3: Batted Ball Distribution, Part 4: Plate Discipline; Part 5, Pull %, Part 6: Lineup Slot and Counting Stats, Part 7: FIP and xFIP; Points League Primer; Using SIERA to Win Your League; How Your Brain Messes with Your Drafts; and Why You Shouldn't Overpay for Saves.

How to Interpret BABIP for Pitchers

The first variable is location, or where a given pitcher pitches. While most fantasy owners are familiar with certain ballparks allowing more or less homers than others, BABIP is an under appreciated component of ballpark factors. Altitude, infield conditions, foul territory, batter's eye and the size of the stadium can all influence how a ballpark plays beyond just home runs.

For example, the Colorado Rockies managed a .348 BABIP at home last season against a road BABIP of .302. Likewise, they posted a .346 figure at home against a .276 mark on the road in 2015, with similar differences in every other season. Players tend to perform a little better at home, but Colorado's splits seem indicative of more than that.

Coors Field is a gigantic ballpark, offering plenty of real estate for balls to find grass. Pitchers claim that breaking balls behave differently due to the elevation of the Mile High City, removing some of their weapons. Fatigue may set in faster for the same reason. The introduction of the humidor has decreased the ballpark's HR rates compared to the complete bandbox it was at the height of the Steroid Era, but it still consistently posts the highest BABIPs in baseball. For that reason, and not dingers, fantasy owners should be skeptical of selecting Colorado hurlers. Colorado is the most extreme example, but every stadium has some quirk that makes it unique.

With location out of the way, we can look at other factors. 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 Kevin Kiermaier and his 25 Defensive Runs Saved (DRS) in just 872.1 defensive innings figures to provide better defense to its pitchers than a team that lacks a platinum glover. DRS is a counting stat like HR or RBI that measures how strong a defender a particular player is, with zero corresponding to an average defender and negative numbers possible for weak gloves. A better defense helps pitchers outperform their FIP.

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 (.239 to .127 in 2016.) 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 fly ball pitcher would love to pitch in front of Kiermaier, while a ground ball specialist would benefit more from an elite infielder like Andrelton Simmons instead.

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 2016, the league average LOB% was 72.9 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.

While defense, park, and sequencing are largely out of a pitcher's control, some pitchers can control their BABIP to a degree. For example, Marco Estrada's .234 BABIP against feels way too low, but he can probably sustain it. First, his 48.2 percent FB% means that many balls put into play against him figure to post low BABIP numbers. Second, he induced pop-ups at a league-leading 16.8 percent IFFB% last season. Pop-ups are almost never hits, so inducing them consistently enables a pitcher to post better than average BABIPs. The same principle holds for pitchers who can limit line drives, but this skill is not quite as sticky as pop-ups. Liners post very high BABIPs but randomly fluctuate, as we have seen in a previous article.

Conclusion

To conclude, a pitcher's BABIP includes some unknown variables but also some predictable inputs. The pitcher's home stadium influences more than just his HR/FB rate. The quality of his defense can help or hurt him. Sequencing does not affect BABIP necessarily, 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. BABIP is just the beginning of that relationship, which will be explored further in Part 9.