Fly Ball Exit Velocity Breakdown
Why it's important, who has it, who doesn't, and who to look out for in 2024.
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The good news is that this is one of my favorite things to do, as evidenced by the fact that… I have been doing it for several years now. Don’t be fooled, there’s no real money in fantasy baseball writing. The top earners in this space probably don’t do much better than pay their mortgage with what they earn. That functions to filter out the people who don’t really love it pretty quickly, the consistent writers are people doing it mostly because they really like it.
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I’m diving into fly ball exit velocity today. The “StatCast era” began in 2015, and since then we’ve all been enthralled with exit velocity, and rightly so!
The numbers have proven what we’ve long known to be true - hitting the ball harder is better.
What is less known, or at least less used, is that exit velocity means a lot more when you’re talking about fly balls as compared to ground balls or line drives. This plot shows you that pretty well:
You aren’t going to find extra bases very often with a ground ball no matter how hard you hit it. And slugging on line drive stays flat pretty much the whole way from 70mph to 95mph. But with fly balls, you see that incline. Hitting a fly ball below 95mph is a bad thing - you don’t want to do that. But hitting a fly ball above 100mph is the best thing you can do. The goal of baseball is, after all, to move runners around the bases - so we want high slugging percentages.
Strikeout rate is very important to consider here. If you average 100mph on your fly balls but strikeout in half of your plate appearances, you’re still going to suck pretty hard.
Let’s take a look at the relationship between the two things we’re talking about while also incorporating those strikeout rates.
Any time you run a scatter plot like this, add the trend line, and see a steep upward [or downward] slope, you know there’s a relationship involved. As average fly ball velocity goes up, so will slugging. Lower strikeout rates will also pull the slugging upward as that leads to more balls in play and more opportunities for hits.
To show this further, let’s go back in history to 2017. In this sample, we find 16 seasons where a hitter averaged more than 99mph on their fly balls (at least 25 fly balls minimum). There are plenty of repeat names, as you’d expect.
Only three examples there of a slugging percentage under .500
Josh Donaldson 2023 (27% K%)
Joey Gallo 2023 (36% K%)
Joey Gallo 2018 (356% K%)
Now, let’s take it the other way. Since 2017, 106 qualified hitters have posted seasons with a slugging percentage above .550. The average average (yes, I said average average) fly ball exit velo in that group is 94.95 miles per hour. The average average fly ball exit velo for the whole sample is 91.34. This would mean that it’s very difficult to post a high slugging percentage without also hitting your fly balls hard.
There are only 13 instances of a hitting going above a .550 SLG with a fly ball velo under 92.
We have a mixture here of
Smaller samples
Elite strikeout rates
Pull-heavy hitters
Good home parks
Even Alex Bregman, who rarely strikes out and knows very well how to pull a homer into the Crawford boxes, hasn’t been able to consistently push out high slugging percentages due to his lack of raw power.
We’ve seen his slugging percentages drop under .450 twice in these last six seasons, and he’s only posted two very strong slugging seasons.
I think my point is well made now, and you can use that interactive dashboard to explore all of the data if you’re so inclined. For now, let’s turn our focus to 2024. Below the paywall, we’ll highlight some 2023 standouts and dig up some potential power breakouts and busts for 2024.