Potential Starting Pitcher HR Rate Regressors — May 27, 2021, A Review by Mike Podhorzer December 21, 2021 Yesterday, I reviewed the pitchers who had most underperformed their Statcast xHR totals through May 24. Today, let’s now review the pitchers who had most overperformed their xHR totals, meaning they allowed fewer home runs than Statcast calculated that they “should have”. Did these pitchers allow a higher HR/FB rate over the rest of the season? Let’s find out. Potential HR Regressors Player HR – Through May 25 xHR – Through May 25 HR-xHR HR/FB – Through May 25 HR/FB – RoS HR/FB Diff Michael Wacha 4 7.5 -3.5 12.1% 19.6% 7.5% Brad Keller 6 8.8 -2.8 16.7% 14.1% -2.6% Germán Márquez 5 7.8 -2.8 14.3% 16.5% 2.2% Daniel Lynch 1 3.7 -2.7 10.0% 11.1% 1.1% Madison Bumgarner 7 9.7 -2.7 10.0% 13.6% 3.6% Mike Minor 8 10.4 -2.4 13.6% 13.3% -0.3% Matt Shoemaker 10 12.2 -2.2 17.9% 31.3% 13.4% Nathan Eovaldi 1 3.1 -2.1 2.1% 10.4% 8.3% Unweighted Avg 12.1% 16.2% 4.2% While the results here weren’t as good as yesterday’s, still six of the eight starting pitchers did indeed post an increased HR/FB rate over the rest of the season. What’s interesting to me is that half the pitchers actually posted a HR/FB rate above the league average as of May 25, so this wasn’t a list of obvious names leading baseball in lowest HR/FB rate. Two of the four pitchers who had already posted a worse than average HR/FB rate were the ones that actually reduced their marks over the rest of the season. Michael Wacha was the list’s biggest overperformer, and sure enough, his HR/FB skyrocketed over the rest of the season. He already has issues preventing hits on balls in play (BABIP below .300 just once since 2016), so adding a high HR/FB rate as well really inflates his ERA. He’s still got the fantastic changeup, so perhaps the Red Sox could get him back on track. Brad Keller already owned the second highest HR/FB rate on the list through May 25, which was well above the league average at the time. He managed to reduce that mark over the rest of the year despite the early overperformance, but he still easily posted a new career high HR/FB rate mark. It was only a matter of time before his mark would correct toward the league average, as he had posted a career 8% mark from 2018-2020. The career best strikeout rate is a positive sign, but it still finished below 20%, and his walk rate regressed. He simply doesn’t own the skills to consider in anything more than AL-Only leagues. Coors Field ain’t easy for pitchers, and I’m not totally sure how home park factors are accounted for in Statcast’s xHR calculation. Germán Márquez was apparently lucky early on, even with a HR/FB rate a bit worse than the league average. He then ended up posting the third highest HR/FB rate on the list over the rest of the way, but finished with a mark almost right in line with his career average. Daniel Lynch had only made three starts when appearing on this list and ended up being demoted to the minors for two and a half months. His HR/FB rate increased a bit after returning, but remained well below the league average. He obviously needs to dramatically raise his strikeout rate to come anywhere near to making good on his prospect promise. After an inflated mark over a small sample last year, Madison Bumgarner’s HR/FB rate dropped back to his previous couple of seasons level. Amazingly, he still continues to post a low BABIP, even as his stuff has clearly regressed. He’s become an extreme fly ball pitcher, so he’ll have to continue suppressing hits on balls in play and home runs on fly balls to have any sort of success. Mike Minor ended up posting almost identical HR/FB rates early on and the rest of the season, both right around the league average. His issues were several, including a decline in strikeout rate and a second straight season with a sub-70% LOB%, which has kept his ERA above 5.00. Though I wouldn’t be thrilled about it, I’m still willing to roster him in an AL-Only league, as his fortune should improve in 2022. It’s pretty crazy to think that Matt Shoemaker may have been lucky to escape with a 17.9% HR/FB rate early on, as that’s already well above the league average. Then you look at his rest of season mark above 30% and you think his MLB career might be over. It took 10 starts for Nathan Eovaldi to finally allow his first home run! That resulted in a microscopic 2.1% HR/FB rate, and we certainly didn’t need an equation or xStat to tell us that mark would rise over the rest of the season. He still ended up posting a HR/FB rate well below the league average over the rest of the way, which is a nice turnaround from 20%+ HR/FB rates over small samples in 2019 and 2020. It took him a while, but he finally turned his premium velocity into an above average strikeout rate. He’ll remain a mixed league asset for as long as he’s striking out a mid-20% rate of batters, for however long that lasts.