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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 get started!
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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. Last year, the decline continued with a league-wide mark of 11.4%. The league benchmark used to be 10%, and we're pretty close to that right now.
Like BABIP, an experienced player's benchmark is a better indicator of his future performance than the league average. For example, AL MVP Aaron Judge is generally regarded as one of the top sluggers in the game today. His HR/FB was 35.6% in 2022, more than triple the league-average rate. If this number regressed to the league average, Judge wouldn't be very good. However, he has a career rate of 32.3%. Clearly, above-average power is something Judge 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 know the next power breakout, so this may be somewhat disappointing. Future power production may be predicted, however, by an increase in FB%. There are limits here, as Myles Straw 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 at least 40%. Subjected to this test, Judge had a 43.5 FB% in 2021. That passes! It also explains why Judge smashed the AL record for HR with 62 after a relatively disappointing 2021 season, as his FB% that year was just 35.5. While Judge improved his HR/FB, the real difference was that he hit a lot more fly balls and put his always outstanding raw power to better use. 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 Jared Walsh and Josh Bell, both of whom finished the season as a bust to some degree. You also would have missed out on the worst season of Juan Soto's career, though the reason why was more his batting average than power production.
We want to be as forward-looking as possible, so that means we have to look at 2022 data to identify potential busts for 2023. A few names that stand out include Joey Meneses (29.7 FB%, 25.5% HR/FB), Michael Harris II (27.1 FB%, 22.9% HR/FB), and William Contreras (31.9 FB%, 27% HR/FB).
It may be jarring to see a name as young and exciting as Harris on this list, but remember that power is only one path to fantasy value. Harris is a premium defender in real baseball who figures to steal bases and post a solid average, giving him a path to fantasy viability 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!
