Potential Starting Pitcher HR Rate Improvers — May 26, 2021, A Review

We’re finally winding down the in-season metric reviews, and today, we return to Statcast’s xHR calculation, but this time for pitchers. So we’ll be reviewing the pitchers that had allowed significantly more home runs than expected according to Statcast through May 24 and find out how each performed over the rest of the season. Like I did for my hitter review, this is essentially comparing HR/FB rates through the first two months with the rest of the season, since actual fly balls are used in the calculation and Statcast is calculating how many of those should have left the park versus what actually did. Let’s find out if these pitchers did enjoy major HR/FB rate improvement over the rest of the way.

Not too surprisingly, nine of the 10 pitchers did improve their HR/FB rates over the rest of the season. The unweighted group average came down from an inflated 20.3% to just above the league average over the rest of the season to 14%. That’s a massive improvement, and since this is a small sample of pitchers, the fact they still posted a mark above the league average over the rest of the season isn’t very meaningful.

Trevor Williams was the biggest underperformer, as one of five pitchers with a HR/FB rate over 20%. This could have looked like a mere repeat of his similar 2020 when he posted a 24.2% mark, but he completely turned things around after that poor start. He missed time due to appendicitis so he failed to record 100 innings, but he ended up posting a lower HR/FB rate than his previous two seasons. Along with a strikeout rate spike, that allowed him to post an improved ERA back below 5.00 and the lowest SIERA of his career.

After a splendid debut in 2020, Triston McKenzie was an exciting target for many fantasy owners heading into 2021. Things didn’t start out very well though as he suffered from gopheritis, he couldn’t find the plate, and his velocity was down. After returning from a stint in the minors, he was much better, including improved velocity. He remains an extreme fly ball pitcher at risk of multi-homers allowed in any particular game, but given that his price may have bottomed, he’ll be a decent speculation in deeper leagues, and could even return to being a shallower league option.

Yikes, so technically Patrick Corbin did improve his HR/FB rate, but it remained above 20% the rest of the season, which is still terrible. He had posted a mark as high as 18.3% in a season once back in 2016, but never higher than 15.3% outside of that year, so this 22.6% season mark was quite the surprise. Combine that with a tumbling strikeout rate and you’re left with an ERA approaching 6.00. Oddly, this was the highest fastball velocity he has shown since 2017 and highest sinker velocity since 2015, while his slider continues to generate a SwStk% above 20%. I wouldn’t completely ignore him just yet, as he could be a nice profit center in deeper leagues given his likely bargain basement cost. He won’t need that much of a rebound to earn his salary.

Incredibly, Anthony DeSclafani’s early HR/FB rate of 10.9%, which was already better than league average, was apparently unlucky according to Statcast! He was the only one who failed to improve his mark the rest of the season, but it barely increased and still remained well below the league average. He could thank his home park, as he allowed just a 5.9% HR/FB rate there, versus a 14.4% mark on the road. I can’t believe Oracle Park is still that good at suppressing homers, so I wouldn’t expect a repeat. Given that he outperformed his SIERA by nearly a full run, he could easily be overvalued next season depending on his cost. But given his home park and defensive support, he probably won’t regress up to his SIERA, so I’d be happy to pay for a high 3.00 ERA, but no better.

It’s hard to believe that Adam Wainwright posted an ERA above 4.00 in each of April and May, and yet finished the season with his lowest ERA since 2014. Given his age, mediocre skills, and SIERA outperformance, he makes for one of the most obvious regression candidates for 2022.

Yusei Kikuchi maintained his 2020 velocity spike and pushed his walk rate back into single digits, yet once again there was something holding back his ERA. In 2020, it was a ridiculously low LOB%. This year, he fixed that, but now his HR/FB rate more than doubled. Sure, he improved from his inflated early season mark, but it still remained very high over the rest of the season. Has it been bad fortune over a small sample? My xHR/FB rate equation actually says no! He simply allows a high barrel rate on the fly balls he gives up. In fact, his barrel rate allowed on fly balls this year was the same as the rate Juan Soto posted! That’s crazy. I have no idea why he has been so prone to allowing such ideally hit fly balls, but he has. Maybe it’s a bad command thing. Still, I’d rather take my chances that his HR/FB rate improves and I end up with a breakout than roster a low strikeout guy I’m hoping maintains a suppressed BABIP.

As a Lucas Giolito owner, it didn’t feel like a vintage Giolito year and it may have been because his extreme inconsistency throughout the season. The high HR/FB rate early on resulted in an ugly 5.68 ERA in April, and while his HR/FB rate after May 24 was actually better than the league average, he posted a 4.06 ERA in June after a sub-3.00 ERA in May. He was clearly affected by the sticky stuff ban as his strikeout rate fell from just over 30% in April and May to nothing higher than 27.7% in any month after. That’s still plenty good, but that was a 27 strikeout difference between 2019 and 2021 in nearly the same number of innings. The lower strikeout rate also increases his ERA and WHIP projections, assuming everything else is stable. It’ll cost him a bunch of dollars in fantasy value.