Introducing Batter xHR/FB Rate, Version 4.0: Std Dev of Dist FB+LD Fun

*The 2021 Pod Projections are now available!*

Now that my xHR/FB rate v4.0 equation has been revealed, let’s dive into the components of the equation and get to know each one of them. We’ll start with Std Dev of Dist FB+LD (SDD), which is the standard deviation of the batter’s fly balls and line drives. This is important because just knowing the average distance of those batted balls isn’t enough. A batter who alternates 400 foot blasts with 200 foot blasts is going to record a much greater HR/FB rate than the batter with consistent 300 foot shots (this batter likely owns a 0% HR/FB rate). Yet, both hitters will post the same average distance of 300 feet. So we need to differentiate between these two hitters, and SDD is how we do it.

First, let’s review the average SDD in my population set by year, which includes all batter seasons since 2015 with at least 10 fly balls plus line drives.

Average SDD
Std Dev of Dist FB+LD
2015 75.8
2016 76.9
2017 77.3
2018 75.5
2019 77.9
2020 75.9

It’s remained pretty consistent each season, bobbing between 75.5 and 77.9. Now let’s check out the hitters with the highest and lowest recorded SDD marks in my entire population set, regardless of how small the sample size was.

Highest and Lowest SDD Marks
Player Season SDD HR/FB
Giancarlo Stanton 2019 106.3 25.0%
Bryan Holaday 2017 28.3 0.0%

You know you’re onto something when Giancarlo Stanton tops a list that correlates pretty well with HR/FB rate! Of course, this was another one of his injury shortened seasons, as he amassed just 59 at-bats and recorded 18 FB+LD, but it’s fun to still see him have no trouble alternating those big blasts with the dinkers. On the other end was Bryan Holaday in 2017, who was as consistent as it gets in just 29 at-bats and 12 FB+LD. His average distance on those balls was just slightly above the league average, which is normally fine. But a tiny SDD means that basically every single one of those 12 batted balls were around that distance, so the odds of any of them going for a homer were nil. Sure enough, he failed to homer.

Now let’s look at the highest and lowest recorded SDD marks in my entire population set, but this time set a minimum number of FB+LD so the sample size is large enough to actually reveal meaningful information. We’ll go with 200+ FB+LD, which equates to around 500 AB.

Highest and Lowest SDD Marks >=200 FB+LD
Player Season SDD HR/FB
Paul Goldschmidt 2017 90.7 24.8%
Didi Gregorius 2016 62.9 10.4%

These marks are much more sustainable over a full season and what you should expect the upper and lower limits to be. The top handful of players each year will typically finish with an SDD in the 85-90 range, while the bottom tier will be between 65 and 70.

Now let’s check out the leaders and laggards of 2020. I’ll set a minimum FB+LD total of 60.

2020 SDD Leaders >=60 FB+LD
Player SDD HR/FB
Marcell Ozuna 91.8 26.5%
Luke Voit 90.4 34.9%
Teoscar Hernandez 89.2 32.7%
Keston Hiura 88.1 26.0%
Chris Taylor 87.0 22.9%
Brandon Lowe 87.0 23.7%

This is a nice list of hitters who truly had banner power years. Amazingly, Luke Voit’s average distance was a foot below the league average, but his alternating blasts with dinks ultimately led to an elite HR/FB. Clearly, the most surprising name here is Chris Taylor. He’s become the new Ben Zobrist, quietly contributing strong value offensively and playing multiple positions.

2020 SDD Laggards >=60 FB+LD
Player SDD HR/FB
Kevin Newman 59.8 2.4%
Mike Moustakas 60.6 17.4%
Victor Reyes 61.9 9.1%
Giovanny Urshela 62.4 14.3%
Robbie Grossman 62.6 16.3%

Whaaaaat, how did Mike Moustakas appear just above the bottom of the ladder here? That’s quite shocking. And yet, he was still able to post a 17.4% HR/FB rate. That was primarily due to his strong average distance. That’s hard to do, because no one averages the distance necessary to hit a home run, so you absolutely must get to that average by hitting much longer flies and liners with your shorter ones. Moustakas didn’t vary his batted ball distances much, but since his distance was so strong, it was enough to still post a solid HR/FB rate.

That concludes our Std Dev of Dist FB+LD fun for today. As a reminder, the metric sported the lowest year-over-year correlation of all the metrics in the xHR/FB rate equation. So although this is definitely a skill, it bounces around more each season than the other metrics. That means that if a hitter’s HR/FB rate spike or decline was mostly fueled by a significant change in SDD, but everything else remained relatively stable, it would probably be best to expect the hitter to revert back to previous season levels as the SDD change isn’t as likely to be repeated.





Mike Podhorzer is the 2015 Fantasy Sports Writers Association Baseball Writer of the Year. He produces player projections using his own forecasting system and is the author of the eBook Projecting X 2.0: How to Forecast Baseball Player Performance, which teaches you how to project players yourself. His projections helped him win the inaugural 2013 Tout Wars mixed draft league. Follow Mike on Twitter @MikePodhorzer and contact him via email.

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Very cool stuff!! Does help explain what I would’ve called ‘unexplainable’ prior to reading this! I don’t know how stupid this may sound: do std deviations shift much from season to season, or are they fairly sticky? I guess, do they stabilize quickly?