# Hitter Statcast xHR Underperformers — May 10, 2021

It hasn’t received a whole lot of fanfare, but Statcast has its own xHR calculation. It defines xHR as Ballparks Gone At/30, though I am unable to find any explanation on how to calculate “ballparks gone at”. The leaderboard does tell us that “environmental variables (elevation/weather/wind/etc…) not factored into these values”, which is essentially an acknowledgement that the calculation isn’t perfect. Environmental factors are real and have an effect on home runs, so you could get most of the way there by ignoring them, you’ll never get all the way there. That said, this metric is seemingly the quickest and easiest way to determine which hitters who have luckiest and unluckiest in the home run department, which is important over a small sample of at-bats. So let’s dive into the biggest underperformers, those hitters whose actual home run total is most below their xHR total.

Below is a list of all hitters whose xHR total is more than one home run more than their actual totals.

xHR Underperformers
Player Actual HR xHR HR-xHR
Trevor Story 4 10 -6.0
Jorge Soler 2 4.8 -2.8
Bryce Harper 6 7.6 -1.6
C.J. Cron 5 6.6 -1.6
Paul Goldschmidt 5 6.5 -1.5
J.T. Realmuto 4 5.9 -1.9
Garrett Hampson 3 4.7 -1.7
Charlie Blackmon 2 4 -2.0
Asdrubal Cabrera 2 3.7 -1.7
Jose Trevino 1 2.6 -1.6
Jacob Stallings 1 2.5 -1.5
Daulton Varsho 0 1.9 -1.9
Yandy Diaz 0 1.9 -1.9

You may have noticed that four Rockies appear on this list. The difficulty in using park-adjusted type metrics with Coors Field is the environmental factors affect exit velocity, while field dimensions actually hamper home run totals. So when an xHR metric is calculated for their hitters, it sees a Coors-inflated EV that looks great in most other parks. However, the bigger dimensions means that EV isn’t as effective, so Rockies hitters look better than they should in this type of calculation. While the calculation hasn’t been shared with me and I cannot be sure my hypothesis is correct, I believe this is the case. I had to deal with this issue when developing my own xHR/FB rate and ultimately decided to just ignore home park since it was too challenging.

So we find Trevor Story way up on the top of home run underperformers. What’s a bit scary for his owners is that his HR/FB rate actually first slipped last year, tumbling into the low teens, and it’s continued its slide this season. He’s also sporting the lowest FB% of his career. However, both his walk and strikeout rates are at career bests, so it hasn’t been all bad. The xHR metric provides optimism even if it pretty clearly is overly optimistic given his home park, while he continues to swipe bases. I’m happy to buy here and wouldn’t even require a discount off his draft day cost.

A pair of Royals sit in the second and third slots in xHR underperformance. I would not have expected Salvador Perez to rank second here with seven homers already and the second highest HR/FB rate of his career. He has already set a new personal high in maxEV, while a decline in FB% provides further potential home run upside if that rises over the rest of the season. However, don’t ignore the increased strikeout rate currently sitting at a career high, which is supported by a surge in SwStk%. He already rarely walks, so more strikeouts means he’ll end up on base even less often than he already is. Just some small warning signs that not everything is rosy here.

With just two homers, Jorge Soler owners have to be a bit relieved to find his name ranked third on this list. His HR/FB rate sits at a tiny 6.5% and since his BABIP is at its lowest in four seasons, you get a sub-.200 batting average. His xwOBA is nearly as high as last year, so he looks like a ripe acquisition target.

Is baseball bored of Bryce Harper? I feel like he’s just never in the conversation of best hitters in the game, probably because a lot of his value is tied to his incredible walk rates. Anyhow, what’s amazing about his appearance here is that his HR/FB rate sits in a tie for the highest of his career, yet Statcast still thinks he’s been a bit unlucky! A rebound in FB% would also add an extra couple of homers over the rest of the way.

C.J. Cron’s BABIP has skyrocketed to .371, which you’d think you could chalk up to the Coors effect, but he has actually posted a higher mark in away parks so far. He has benefited from his home park in the power department though, posting a HR/FB rate more there more than double his away mark. Still, aside from his batting average, it hasn’t yet been a Coors-inflated offensive outburst. It’s only been 93 at-bats though overall and 54 at home, so there’s time for Coors to do its thing.

Fantasy players kept waiting for Garrett Hampson to win a starting job somewhere, but can you really blame the Rockies for not just giving one to him? He owns a career .300 wOBA and that’s Coors-aided! He simply just can’t hit and has only been a positive defensively in center field. That said, he clearly has serious fantasy potential as long as he’s earning playing time and Statcast’s xHR mark suggests he should be back in double digits in HR/FB rate to go along with his steals.

Charlie Blackmon makes for the fourth Rockies hitter on the list and at age 34 and coming off a disappointing 2020, it would be easy to believe the end is near. I’m not so sure though. His xwOBA is back up to .372, which is actually the highest it’s ever been since the calculation began in 2015, his walk rate sits at a career best, while his strikeout rate is at its lowest since his 2011 debut over a small sample. I think he looks like a pretty darn good trade target and he shouldn’t actually cost a whole lot anymore.

Well hey now, at least someone or something is bullish on Yandy Diaz’ home run potential! He’s still failed to homer through 108 at-bats, even though his FB% has more than doubled from bottoming out last season. I still can’t comprehend how a hitter with those muscles doesn’t hit for more power when he does get the ball in the air. At least he’s been an OBP league monster, but he’s done nothing in the counting stats. He’s like the Mallex Smith of OBP — how much do you value a one-category stud?!

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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the ghost of tyler chatwoods control

Do you mean Trevor Story’s HR/ FB rate started slipping last year as opposed to yesterday?