Last 30 Day Starting Pitcher Strikeout Rate Decliners — Jul 22, 2021

Yesterday, I discussed six starting pitchers who had seen their strikeout rates surge the most over the last 30 days compared to the rest of the season to date. Today, we’re going to review the starting pitchers on the opposite end — those whose strikeout rates have declined the most over the last 30 days.

After an exciting first couple of months of the season, Joe Musgrove now heads our strikeout rate decliners list over the last 30 days. One of the glaring issues is that he has lost some velocity on all his pitches. It’s not a significant amount of velocity, but it is a velocity loss at a time when the average pitcher should be expected to slightly gain velocity. The velocity loss undoubtedly led to a drop in SwStk% marks, as he just posted a single digit mark in two straight games for the first time all season. It doesn’t appear to be a spin rate issue as he hasn’t loss any significant amount of spin over the last month on any of his pitches after the ban on stick stuff. Could this all be because of the marginal, but meaningful, loss of velocity? It’s hard to believe, but something is clearly going on that’s worth monitoring.

Mike Minor finally had a solid outing two days ago and one in which he allowed fewer than four earned runs since early June. Oddly, he has essentially given up on his changeup, as he went from a 21.2% usage to seeing that rate drop in each subsequent start over the last 30 days. It’s weird because historically, it’s been his best whiff pitch. It hasn’t been a velocity issue, as his last 30 day fastball velocity is almost identical to the previous period. In terms of spin rate, his changeup had been trending down all season before spiking in his last start, so it’s hard to blame that on his struggles, but perhaps he has thrown it less recently because of the decline in the pitch’s spin rate. He’s a tough one to pinpoint, but the bottom line is his overall season ERA is more than a full run higher than his SIERA, mostly because of a super low LOB% that you’d have to assume will rebound toward his career average.

Kolby Allard opened the season n a relief role, so it’s no surprise that his strikeout rate has tumbled as a starter. His velocity actually hasn’t been affected by the move, but his swing and miss stuff has been extremely inconsistent from start to start. He has alternated between double digit SwStk% marks and mid-single digit marks as low as the 5.7% mark he posted during his last start. With improved control, he looks a lot better than last year, but he might be better suited in relief.

LOL at Jacob deGrom making this list and his last 30 day strikeout rate still sitting at 38%.

Ditto for Corbin Burnes, who even during a decline phase, has still managed a 31.1% strikeout rate.

Ate age 41, Rich Hill might finally be feeling the effects of his age. His velocity is down over his last 30 days and his fastball dipped to an average of just 86.8 MPH last start, nearly two MPH less than he has averaged during the season. His curveball also sat 2.5 MPH lower than it has all season. It hasn’t only been his velocity. Both his four-seamer and curveball have lost significant spin, which is obviously suspicious given the recent ban on stick stuff. Given Hill’s declining velocity and spin rate, it’s not hard to proclaim he won’t be a fantasy asset over the rest of the season, regardless of league format.

Sandy Alcantara has actually gained velocity over the last 30 days, posting his two highest average velocities during the period, including his last game at 99 MPH. So clearly velocity isn’t the issue here. Instead, he appears to be another spin rate victim as all his pitches have lost meaningful spin over the last 30 days. It has really hurt his changeup, as the Whiff% on that pitch has declined significantly in his last five starts. In fact, his Whiff% hasn’t exceeded 25% in those games, and actually hasn’t reached 30% at all since June 1, compared to April and May in which he never posted a mark below 30%, and reached as high as 54.5%. So it seems his strikeout rate this year has really followed his changeup’s effectiveness.

Finally, we finish with Alex Cobb, who has actually only made four starts during the last 30 days, so his sample is a bit smaller than the others. His splitter usage has been quite inconsistent with no discernible trend, but his velocity has looked good, so no explanation there. Unfortunately, he looks to be yet another spin rate victim. His sinker’s spin rate has lost 150-200 RPM, while his splitter has essentially lost 300 RPM. That’s crazy! The other concern, possibly related to the loss of spin, is that he has induced a sub-40% GB% in three of his last four starts. As an extreme groundballer, posting a sub-40% GB% in any particular game is infrequent, so to have done so three times in four games is surprising. In fact, he had only posted a sub-40% GB% once all season before the last 30 day period. As a Cobb owner in a shallow mixed league, this analysis has opened my eyes and will make me think twice not only about keeping him active, but keeping him on my team at all.