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The most accessible of the fantasy-relevant advanced stats is BABIP, or Batting Average on Balls In Play. It simply measures a player's batting average on balls in play, with outcomes such as strikeouts and home runs removed from consideration. In general, the league average hovers around .300, a nice round number to remember. However, it has been trending downward in recent years with 2023's figure coming in at .297.
Many know BABIP as an approximation of luck, with either a very high or very low number indicative of a major batting average regression in the future. That is partially correct -- the stat can be used to predict batting average fluctuations. However, a player's skills may allow him to consistently run a better-than-average BABIP, or doom him to a consistently below-average figure.
There are two primary sources to look up a player's BABIP: FanGraphs and Baseball Reference. They don't always have the same numbers, and FanGraphs tends to be preferred because the site lets you look at BABIP by batted ball type (more on that below). Just type in a player's name in the search bar provided and his BABIP is displayed in the first chart that pops up. Now that you know where to find BABIP, let's explore how to use it.
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The Above-Average BABIP Formula
If you want an example of a batter who sustainably runs high BABIPs, look no further than Julio Rodriguez. Rodriguez hit .275/.333/.485 with 37 SB thanks in part to a .330 BABIP more than 30 points better than the league average last season. If we regressed his BABIP to .297, Rodriguez would not only help fantasy managers less with his average but have fewer opportunities to steal a bag. The Mariners superstar would become pedestrian as a result.
Fortunately for Rodriguez, much of his BABIP boils down to sustainable skills and not dumb luck. His career BABIP is .336, six points higher than last year's mark. As the 37 SB suggests, Rodriguez can also fly. He can turn groundouts for other players into singles, giving him a consistent source of base hits to prop up his BABIP and overall fantasy value. Of course, running fast doesn't mean that Rodriguez couldn't be fortunate or unfortunate in any given season. How can fantasy managers tell the difference?
Looking at BABIP by batted ball type can be a great tool for examining this. Rodriguez gets his speedster hits exclusively on grounders, as footspeed does nothing to prevent a fielder from catching an airborne ball. While the league averaged a .243 BABIP on grounders in 2023, Rodriguez posted a .297 mark on them. His career rate is even better at .317. Therefore, we can conclude that Rodriguez should continue to dramatically overperform the league average BABIP on ground balls in 2024 and beyond.
Rodriguez's wheels won't help his BABIP on fly balls or line drives. Rodriguez's .106 BABIP on flies was short of the league's .117 mark, so he might get a couple of extra hits on them this year. However, his .750 BABIP on line drives bested the league's mark of .702, likely costing Rodriguez more hits than he'll gain from flies. As such, we should expect Rodriguez's overall BABIP to decrease slightly while still beating the league's mark handily.
BABIP takes multiple seasons to stabilize (or become predictive), and you need to avoid rushing to conclusions when using it. A rookie who posts a .380 BABIP should not be expected to keep it up because that's suddenly his baseline. That said, an established player's baseline is more predictive of future performance than the league average barring other factors changing.
The Below-Average BABIP Formula
The same trend is possible in a negative way. For example, fantasy managers know Max Muncy as a potential power source who will drain your roster's batting average thanks in large part to a consistently low BABIP. Last season, Muncy posted a BABIP of just .221 and a batting average of .212, creating batting average upside if you think it will regress to .297. Unfortunately for Muncy, that isn't happening.
Muncy hasn't posted a league-average BABIP in his entire eight-year MLB career:
While Rodriguez's speed grants him base hits, Muncy's average speed means that he is retired on grounders that Rodriguez can beat out. He also hit just 7.1% of his ground balls to the opposite field, allowing opposing defenders to cheat to one side with an infield shift every time up. The result was a .170 BABIP on grounders in 2023 right on par with his .173 career mark.
That's not the end of Muncy's BABIP problems though. He also hit an above-average number of pop-ups in 2023 with a 13.3 infield fly ball (or IFFB%) rate last season. Pop-ups are nearly always caught with minimal difficulty, so players who hit a ton of them tend to run low BABIPs. Sure enough, Muncy's career BABIP on flies of .095 looks great compared to the .062 he put up last season.
It's easy to see why Muncy struggles with BABIP season after season. That won't change in 2024.
Conclusion
To conclude, BABIP can be used to indirectly measure a player's batting average luck by comparing it not to the league average, but to an established player's career number. Younger players without an established baseline are generally regressed to the league average, but these predictions are less reliable than those based on a player's personal history.
Footspeed, batted ball authority, line drive rate, and defensive positioning all give players some ability to manipulate BABIP. Players with these skills may still overachieve, and this regression can be analyzed by examining BABIP by batted ball type. Our next installment will look at HR/FB and why it is sometimes called the BABIP of power.
