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Using BABIP to predict a player's batting average is great. Batting average is a category in many league formats, and every hit is an opportunity to steal a base or score a run. Most fantasy managers find the long ball sexier, though.
Every HR comes with a guaranteed run scored and at least one RBI. Many managers build their teams around power for this reason. Yet, fluky HR campaigns can happen just as easily as fluky batting average ones. How do we tell the difference between a legitimate breakout and a fluke?
The answer boils down to two metrics: HR/FB (sometimes stylized as HR/FB%) and FB% (or what percentage of a batter's batted balls are fly balls as opposed to grounders or line drives). FanGraphs is the best place to find both of these metrics, though you will have to scroll down to the fifth graph on each player's page (labeled "Batted Ball") to see it. Without further ado, let's review how to use HR/FB!
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How to Interpret HR/FB
HR/FB measures the percentage of fly balls that leave the park. In 2019, a power-friendly baseball contributed to 15.3% of all fly balls ending up in the seats. That number declined slightly to 14.8% in the shortened 2020 season and declined further to 13.6% in 2021. In 2022, the decline continued with a league-wide mark of 11.4%. The trend began to change last season, with the league-wide HR/FB increasing to 12.7%.
Like BABIP, an experienced player's benchmark is a better indicator of his future performance than the league average. For example, AL MVP Shohei Ohtani is generally regarded as one of the top sluggers in the game today. He slugged 44 HR in just 135 games last year, after all.
Ohtani's HR/FB was 31.2% in 2023, about 2.5 times the league average. If this number regressed to the league average, the Dodgers would have wasted $700 million. However, Ohtani has a career HR/FB rate of 27.6%. Clearly, above-average power is something Ohtani just does.
Large spikes or dropoffs in HR/FB are generally temporary, meaning that the stat is usually not predictive of a power breakout. Fantasy gamers want to find power breakouts, so this may be somewhat disappointing. However, future power production may be predicted by an increase in FB%. There are limits here, as Esteury Ruiz is never helping a fantasy team with his power no matter how many fly balls he hits. Still, FB% is generally the stat you want to look at for power potential.
What Is a Good FB%?
Elite sluggers generally post a fly ball percentage of around 40%. Subjected to this test, Ohtani had a 39.5 FB% in 2023. He technically fell just short, but Ohtani bested his career FB% of 35.7 en route to his best power season on a per-game basis. He should continue being a force at the plate so long as he keeps elevating baseballs.
Using the discrepancy between a player's HR/FB and FB% can be a great way to identify potential fantasy busts. Reading this column last year would have spared you from investing in Joey Meneses, who was below replacement level last season. It also would have warned you that Michael Harris II and William Contreras were both primed to disappoint in the power department.
Harris II got off to a nightmarish start before rebounding, but he still fell one homer shy of his NL Rookie of the Year season despite logging 98 more PAs. Contreras was an even better example of HR/FB regression as he went from 20 HR in 376 PAs to 17 HR in 611 PAs. Both were still useful in fantasy, but you were disappointed if you were expecting huge power numbers.
We want to be as forward-looking as possible, and that means looking at 2023 data to identify potential busts for 2024. A few names that stand out include Edouard Julien (31.4% HR/FB, 23.9 FB%), Jesus Sanchez (20.9% HR/FB, 26.5 FB%), and Elly De La Cruz (24.5% HR/FB, 21.8 FB%).
It may be jarring to see a name as young and exciting as De La Cruz on this list, but remember that power is only one path to fantasy value. Elly De La Cruz has electrifying tools on the bases and in the field, giving him the potential to be a fantasy stud even if his power declines substantially. Still, you should consider the risk of a power decline before paying a premium.
Conclusion
HR/FB is considered the BABIP of power because it can be used to evaluate whether a given player is outperforming his true talent level. A player with a large spike or decline in HR/FB should generally be expected to return to his established baseline moving forward. Ballpark factors may alter HR/FB, but in general, raw fly ball percentage is a better tool to identify potential power breakouts.
Of course, it is possible for a batter to legitimately change his approach and permanently boost his HR/FB. Statcast allows us to measure precisely how hard a player is hitting the ball, potentially validating a performance that would otherwise be labeled a fluke. Check out later articles in this series for more information!
