May 2021 Starting Pitcher Velocity Decliners

Yesterday, I listed and discussed eight starting pitchers who have gained the most fastball velocity in May versus April. Let’s now check the flip side — those pitchers who have lost the most velocity in May compared to April. This could be the first warning sign of a reduced level of performance, or worst case scenario, injury.

In April, Adam Wainwright was making us remember his top prospect days many seasons ago. His fastball velocity jumped over 90 MPH for the first time since 2017, while his strikeout rate stood higher than he ever finished with in a season, supported by what would be a career best SwStk%. Then it all crashed down in May, as his velocity dropped back below 89 MPH, bringing down both his strikeout rate and SwStk%. Even in an NL-Only league, I’d prefer the greater safety from a good middle reliever.

Marcus Stroman rarely throws his four-seamer, so the decline here means little. However, his sinker velocity is down a touch, but not the degree in which his four-seamer is as shown in the table. Either way, what we do know is that despite marginally increasing his SwStk% in May, his strikeout rate has plummeted. He has never been much of a strikeout pitcher to begin with, but his May rate was lower than he ever posted over a full season. The good news is his SwStk% easily sits at a career high, so the strikeouts could and should return, but offsetting those whiffs is a career low called strike rate. I’d choose to focus on the career best SwStk% and happily hold if I were an owner.

Joe Musgrove came out throwing harder than ever before, but he couldn’t keep it up past April. His May velocity is now right in line with his full season 2020 and both his strikeout rate and SwStk% have returned to more sustainable levels, rather than the elite marks he had posted. For the season, his strikeout rate and SwStk% are almost identical to his 2020, but I would lean more toward his May marks as his true talent level.

Anthony DeSclafani was quite the pleasant surprise in April, even though his fastball velocity was down compared to 2019 and 2020. Then he lost some velocity in May, and suddenly he’s sitting below 94 MPH for the first time since 2018. Predictably, his strikeout rate and SwStk% have dropped and make him far less interesting. He’s still worth monitoring given his home park, but I liked him a whole lot more throwing near 95 MPH then below 94 MPH.

After two poor seasons, the Dylan Cease breakout has now arrived. I wouldn’t get too too excited yet though, as his SIERA is nearly 4.00, and significantly above his current 2.41 ERA. His control is still poor, but at least he has finally turned his high velocity fastball into strikeouts. The interesting thing here is that his velocity, which was already down in April compared to last year, dropped even further in May, and yet his strikeout rate and SwStk% both jumped! He certainly has enough velocity, even at a reduced level, to not be too concerned though.

Just like Cease above, Brandon Woodruff lost velocity in May, and yet both his strikeout rate and SwStk% surged higher. Unlike Cease, Woodruff’s April velocity was a career best, and continued his trend of increasing his velocity every single season. In May, his velocity regressed back, but still was within a normal range of his 2019 and 2020 seasons. His performance trend has been pretty incredible. Aside from the ever-increasing velocity, his strikeout rate and SwStk% have increased every season.

Tyler Mahle’s fastball velocity shot up to a career best in April, and while he lost some juice in May, that mark still represents higher than he’d posted over a full season previously. Last season was the first in which Mahle really turned that velocity into strikeouts, but this year, that only carried into April, as he lost his whiffiness in May. Mahle does rely on called strikes at a higher level than most other starters, but to be a real strikeout contributor, he’ll need to keep his SwStk% in double digits.