Getting to Know Batter Average Fly Ball Distance

Last week, I unveiled the newest version of my xHR/FB rate, which incorporates two Statcast metrics. The first of those components was Barrels per True Fly Ball Rate (Brls/True FB), which I introduced last Wednesday, and then discussed further on Thursday. Today, I’m going to dive into the other Statcast metric, Average Fly Ball Distance (Avg FB Dist), which is found on the Statcast Search page.

The irony is that Avg FB Dist was actually one of three components of the original xHR/FB equation I developed three years ago. After axing it for a completely skills-based second version, I have brought it back into my improved formula (it’s not exactly the same as the original, as the sources are different, and so are the averages). We’ll get to why shortly, but first, let’s check out some correlations:

Not surprisingly, Avg FB Dist strongly correlates with HR/True FB and HR/FB. That’s a total duh, as the further a batter hits the ball, the more homers he’ll hit, all else being equal! What also fails to shatter the earth is the high correlation with Brls/True FB. Obviously, barreled balls, by nature of its definition combining exit velocity and launch angle, travel further than non-barreled fly balls on average. In general (but not always), the more barrels hit, the further the average fly ball distance.

So given the high multicollinearity we have between these two variables, it might be questionable to use both. In this case, though, it’s not. The addition of Avg FB Dist actually provides additional and necessary information. Let’s check out another table, this time pitting seasonal averages of Brls/True FB and Avg FB Dist next to each other for my population sample (60 BBE for each season, 2015-2017).

Aha! If you recall last week, the current leaguewide power spike really manifested in 2016 (actually, the second half of 2015), and we see that in both the Brls/TFB and Avg FB Dist surges. You also might remember that I called out 2017 for a dip in Brls/TFB, which was curious given that the HR/FB rate took another significant step up. A rising Avg FB Dist at least somewhat helps to explain how a lower Brls/TFB rate could possibly yield more home runs.

We think we know about secretive changes to the baseball, which is resulting in greater distances, given the same underlying swing variables, such as exit velocity and launch angle. So essentially, barrels, and really all fly balls, are traveling further, even if batters aren’t actually hitting more balls that qualify for the barrel classification. It could be that the balls have less drag, allowing the ball to fly further, or batters are optimizing their barrels, so they travel further and jump over the wall with more frequency. Or perhaps something else.

Whatever the explanation truly is, or if it’s a combination of several, Avg FB Dist acts as a proxy for all that extra stuff. It’s the “hey, Player X’s Brls/TFB rate is lower than Player Y’s, but his fly balls have actually averaged a greater distance, suggesting he’s doing something else good that we cannot quantify just yet.” Initially, it was recommended I add a seasonal coefficient to my xHR/FB equation to handle the HR/FB rate surge, but Avg FB Dist does the trick, and does so much more effectively. Rather than assign the same seasonal variable to every player for that season, we could use the exact extra stuff each batter added to justify his HR/FB rate.

For context, let’s take a look at the range of Avg FB Dist marks batters have posted over the last three years.

Can you guess who that 386 foot max fly ball distance belongs to? Believe it or not, it’s not Aaron Judge. It was actually posted by former former former top prospect Brett Wallace in 2015. Of course, the sample size was tiny with just 20 fly balls, but it does confirm that he did have some power in that bat. Gary Sanchez during his epic 2016 run actually sits second at 380 feet, then there’s a gap to 366 feet, before finally getting to the first name that endured a full season – Giancarlo Stanton in 2017 at 358 feet.

Establishing the minimum is poor Eury Perez’s 2015 season, though that came from just 15 fly balls. The first full-timers toward the bottom are a pair of no-power speedster Billys, Hamilton and Burns, posted back in 2015.

As discussed, for now we are using Avg FB Dist as a proxy for all the other unquantifiable things a batter is doing to increase their distance, that isn’t exit velocity or launch angle. We know that horizontal launch angle, or spray, is a factor, but that’s still unavailable. We also learned about spin, which supposedly has a dramatic effect on distance. The next frontier is using that data when/if it becomes available and reverting back to a completely skills-based equation (since Avg FB Dist is a result, not a process/skill).