Joining the Fly Ball Revolution — Apr 19, 2021, A Review

Why do we care about a batter’s fly ball rate? Because all else being equal, a higher fly ball rate will result in more homers, so paying attention to a hitter’s batted ball profile is important. Typically, analysis centers around a hitter’s raw home run total and whether it’s higher or lower than expected at any point during the season. Sometimes, we see HR/FB rate thrown in as well to assess how real the home run surge or collapse might be. But fly ball rate, or FB%, is just as important, as it’s one of the three drivers of home runs, along with strikeout rate and the aforementioned HR/FB rate.

In mid-April, I looked at the hitters who had increased their FB% most versus 2020 as a potential early sign of a home run breakout. Let’s find out how they did over the rest of the season.

Can you say regression? Out of the 23 batters who had increased their FB% marks by at least 10% through Apr 17 versus 2020, just two of them avoided a decline over the rest of the season compared to that early season surge. Just over half (12) of the batters lost double digit FB% over the rest of the season compared to their early season marks.

In the Diff column, I highlighted those batters who I arbitrarily decided still held enough of their gains over the rest of the season to consider the early FB% spike actionable. That includes two hitters who gained just less than 5% from 2020, which I think is bordering on meaningful and not meaningful. So with that definition, that still gave us 10 batters who over the rest of the season did settle in at a much higher FB% than 2020, even if that level was well below what they did through Apr 17. Let’s now discuss those 10 batters.

After a poor start in Tampa, Willy Adames was shipped off to the Brewers where he surged. He set a new FB% high and it led to his highest home run total yet, and a AB/HR mark that improved once again, continuing its trend of decline (that’s a good thing) since his 2018 debut. All his other home run related drivers remained stable (welllll, he did post a strikeout rate rebound compared to 2020, but merely came back to his 2020 levels), so this was all about the FB% spike. It’s anyone’s guess if he has established a new level and we could expect another 40% mark moving forward, or this was a one-year wonder and he’ll be back around 30%. His power potential will heavily depend on where he lands.

I certainly didn’t expect 33 homers from Ryan Mountcastle during his first full season. While he did post the highest HR/FB rate of his professional career, he also pushed his FB% above 40%, to a level he’s posted at times in the minors. I would bet on some slight regression here, but I imagine a full season should result in a 30-homer lock. There’s even some additional upside if his strikeout rate rebounds, and does so without hampering his power.

I simply can’t explain how Joshua Fuentes earned 284 PAs with a .261 wOBA playing half his games in one of the premier hitter’s parks in baseball. The FB% spike should have done wonders, but his HR/FB rate collapsed into single digits, erasing any FB%-related gains.

This was merely a rebound for Randal Grichuk, who had just posted his lowest FB% in 2020, the first time it slipped below 40%. That his strikeout rate improved again to another career best was a great positive, but it was undone by a collapse in HR/FB rate, which fell to the lowest of his career since his small sample 2014 debut. Without looking any deeper, I would imagine that mark should rebound next year.

Joc Pederson’s FB% has fluctuated between the mid-to-high 30% range into the low-40% range, so while this represented an increase versus 2020, it wasn’t anything new for him. Like Grichuk, the FB% rebound was good to see, but his HR/FB rate fell to a career low. Again, having not looked any deeper yet, it would seem like a rebound is a likely.

Gosh Yandy Díaz, you are such a tease. We thought it was just a matter of getting his balls in the air and then a mixed-league worthy season like 2019 would happen. But this time, his HR/FB rate fell to barely into double digits, so the rebound in his FB% off that hilariously low 2020 mark wasn’t fully taken advantage of. He remains Joe Mauer, without the catcher eligibility, or Mauer when he was a first baseman. Solid in OBP leagues, but you’ll have to find your power elsewhere.

It’s hard to believe that this was the first time Tommy Pham pushed his FB% over 30%. He’s another who has the power to take advantage of a much higher FB%, but simply doesn’t. Sticking on a familiar theme, he too offset the jump in FB% by posting a career low HR/FB rate. In fact, that mark has now dropped every single season since 2016. That’s five straight declines! That’s hard to do. At least he still steals bases, but at age 34 next year, you have to wonder how long that will last.

We witnessed another career high FB% rate, this time by César Hernández. This was another notable one as he also posted a career best HR/FB rate, with just the second double digit mark of his career. Combined, it resulted in his first 20-homer season. But with no speed and the lowest BABIP of his career (actually below .313 for the first time), those extra homers didn’t exactly make him a more valuable fantasy asset.

David Fletcher was another whose 2021 FB% spiked, but it was only off a down 2020. His FB% actually finished below his 2018 and 2019 marks. As a low power guy, he really shouldn’t be hitting a lot of fly balls anyway. Typically a batting average an OBP asset, his BABIP fell below .300 for the first time, and combined with a tiny 1.3% HR/FB rate, it meant his lowest batting average and OBP of his career. At least he stole 15 bases out of nowhere, which is surprising given how less frequently he was on base this season!