Starting Pitcher Fastball Velocity Decliners — 7/28/20, A Review

Yesterday, I reviewed how the starting pitchers that increased their fastball velocities the most after their first start fared over the rest of the season. Today, let’s check in on the velocity decliners. Since the article was typed on July 27, that means it includes velocities through July 26. Did these pitchers rebound off their first start declines?

My first reaction when I see a significant dip in fastball velocity is that the pitcher must be injured. Sure enough, of the nine pitchers that lost at least two miles per hour on their fastball in their first start, six of them ended up on the IL due to some sort of injury. That’s a high injury hit rate and why it’s so important to monitor velocity in every start.

Overall, of the 23 velocity decliners after their first start, eight up them posted a velocity within 0.3 MPH of their first start velocity over the remainder of the season. That means there was essentially no rebound and all you needed was one start’s velocity to know their velocity would be down all season. Only four pitchers saw their velocity over the rest of the way rebound to within 0.3 MPH of their 2019 mark, while one actually ended up posting a jump of 0.8 MPH over 2019 the rest of the way (Freddy Peralta).

As many of you were, I was a fan of Mitch Keller heading into the season as a prime sleeper after posting an ugly 7.13 ERA in his 2019 debut, but with strong skills en route to a 3.78 SIERA. Unfortunately, his velocity collapsed and he eventually landed on the IL with an oblique strain. His velocity regained most of its losses upon his return, but was still down from 2019. But now he ended the season with more walks than strikeouts and a 6.94 SIERA! With a 2.91 ERA, it’s likely he finds his way onto many sleeper lists again, but this time he’s far less deserving. Then again, the 21.2 inning sample size is tiny, so it might be better to ignore just about everything in his 2020 line.

Madison Bumgarner’s velocity remained under 89 MPH all season, and as you could imagine, that’s not the type of velocity that’s going to lead to good results. He missed time to a back injury, which might explain the velocity dip, as his strikeout rate plummeted into the mid-teens. Even though he posted a 6.48 ERA, it wasn’t that much higher than his 5.31 SIERA. I’m real curious to see how he gets valued and he he performs next year, as most have given up on him after his recent skills slide, and his 2020 might be the icing on the cake to completely ignore him.

James Paxton made it just five starts with diminished velocity before his season ended with a forearm injury. Interestingly, his peripherals remained in tact, as it was a combination of inflated BABIP and suppressed LOB% that raised his ERA to 6.64. If he enters next season healthy, there’s a good chance he ends up a bargain.

Charlie Morton late career renaissance driven by a velocity spike and strikeout rate surge was pretty amazing to follow. But he’s 36 years old now and the injuries could pile up, while the velocity continues to decline. He’ll be a risk next year, even at a likely discounted price.

Not only did Zack Greinke’s velocity fail to rebound after that first start, it actually declined further the rest of the way! And yet, he still managed to post a three year high in strikeout rate and maintain his SwStk%. It’s unbelievable. His BABIP jumped over .300 for the first time since 2014, which paired with a sub-70% LOB% (first time since 2011), pushed his ERA above 4.00. At some point, the weak velocity has got to affect his strikeout rate….right?!

I think one of the quieter disappointments this season was Patrick Corbin. After a two-year spike in strikeout rate, that mark plummeted to its lowest since 2016. His pitch mix remained the same, but his fastball velocity hit a career low. Now the question is whether his 2018-2019 strikeout rate was the unsustainable performance, or was 2020 just a crazy season down year that we shouldn’t put much weight on? I’ll be curious to see his price next year.

A decline in velocity had no effect on Aaron Nola, who ended up posting career bests in both strikeout rate and SwStk%. He also totally changed his pitch mix, throwing his four-seamer and curveball less often, in favor of his sinker and changeup. Given the pitches’ respective SwStk%, that change doesn’t necessarily look like a big strikeout rate booster, but instead, it was simply because his top three pitches all registered SwStk% marks well above his career average. I’m guessing his strikeout rate and SwStk% marks revert back to his pre-2020 days, or at least close to it, next year.

Mike Clevinger opened the season with decreased velocity, but completely rebounded after that first start. His underlying skills took a hit though, as his SIERA surged more than a run higher from his 2019 level to 4.36 and his strikeout rate hit its lowest since his 2016 debut. However, an unsustainable 85.9% LOB% and low .275 BABIP saved his ERA, making him look like the same pitcher he has been. Given his history, it looks like his 2019 was the outlier in terms of strikeout rate and SwStk%. He’ll need to continue posting a better than average BABIP and high LOB% to be among the top tier of pitchers. I’d rather bet on the peripherals driving ERA than the luck metrics being maintained, meaning I’m highly unlikely to own Clevinger.

Freddy Peralta was one of just two pitchers who posted a strikeout rate that was higher than 2019 over the rest of the season after their first start. Of course, he spent the majority of the season in the bullpen, so that certainly explains the rebound. This season, he apparently introduced a slider that he threw over 20% of the time, at the expense of his fastball and curveball. I always wondered how he has been such a strikeout machine when he threw his fastball so frequently, so adding a third pitch is a big deal here. The slider was fantastic, as it posted a 20.8% SwStk%, easily his best whiff-inducing pitch. As dominant as he was out of the bullpen, the slider makes him much more interesting as a candidate to rejoin the Brewers’ rotation.