Interesting Last 30 Day Starting Pitcher SwStk% Laggards — Through Jul 17, 2023

Yesterday, I highlighted and discussed four starting pitchers ranking high on the last 30 day SwStk% leaderboard. Let’s now flip to the other end of the leaderboard — those starters who surprisingly find themselves closer to the bottom.

Mitch Keller | 6.1% SwStk%

Early in the season up to the last 30 days, Mitch Keller was enjoying a true breakout season. It has been something we have been waiting for for some time now. He had posted a 28.3% strikeout rate, while maintaining the velocity spike he experienced last year.

As a Keller owner, I was spooked by a below average SwStk%, so ultimately traded him away earlier in the season. That SwStk% sat at just 9.6% up until this last 30 day period, which certainly doesn’t match with a near 30% strikeout rate. So my concern was that eventually, his called and/or foul strikes would decline and bring his strikeout rate back down, resulting in increased ratios.

What I didn’t foresee was his already below average SwStk% plummeting. He has now posted the lowest SwStk% among qualified pitchers over the last 30 days! In fact, he hasn’t posted a double digit SwStk% game in his last seven starts, and has finished at or below 3.0% twice! One issue is he has lost some fastball velocity, averaging 95 MPH with his four-seamer versus 95.7 MPH earlier, while his sinker and cutter velocity have dipped as well. Obviously, averaging 95 MPH is still better than the average starter, but even with his peak velocity, he couldn’t crack a double digit SwStk%.

He has still been posting decent enough results to maintain trade value. If I still owned him, I would definitely be looking to trade him away as it’s hard to believe he’ll deliver strong value while generating so few whiffs.

Jon Gray | 7.2%

Wow, Gray has gone from a 12.9% SwStk% earlier in the season to just this 7.2% mark over the last 30 days. Interestingly, it merely brings his season SwStk% down to his career average and in line with his recent past. So even for pitcher SwStk%, regression to career average is a strong force. That early season 12.9% SwStk% represented a career best at age 31. So did anything change in the last 30 days or did he seemingly just end up with worse results as his luck shifted?

Over the last 30 days, he has thrown his changeup far less frequently and his already heavily used slider even more. Normally, that would increase SwStk% as sliders carry a higher mark on average. Gray is no exception, as his slider’s career SwStk% is nearly double his changeup’s, and its current season mark is well above as well. His velocity has been stable as well, with the only real change coming from his slider…which he is actually throwing harder now.

So it’s not really clear from his pitch mix and velocity what’s causing the decline in SwStk%. After five straight double digit SwStk% marks, including the last of those starts coming as the first start in the last 30 day period, he has now reeled off four straight starts with a SwStk% no higher than 8.2%. If I rejigger the time periods so I include his first start from the last 30 day period into the early season period, I find even less change in pitch mix and velocity!

Without any clear explanation for the decline in SwStk%, I’ll just chalk this up to his string of lower marks just so happened to come in a row over the last 30 days while I am reviewing them. However, owners should realize that his strikeout rate sits at a career low, below 20% for the first time (excluding the short 2020 season), and he’s massively overperforming his SIERA and xERA. A career low called strike rate is most of the culprit here, which I figure will improve.

Logan Webb | 8.2%

Ever since a breakout 2021, fully supported by his underlying skills, Webb has been an excellent fantasy pitcher. Of course, he lost some whiff ability last year and his strikeout rate dropped, but he was able to parlay a single digit HR/FB rate into a sub-3.00 ERA, despite a mid-3.00 SIERA. This year, the results have been more of the same, while his strikeout rate has rebounded, even in the face of a drop in SwStk%.

That drop in SwStk% has increased over the last 30 days, as its gone from 9.8% to 8.2%. While he’s mixed in two games of double digit SwStk% in the six starts that make up his last 30 days, he has also posted just a 4.7% mark and a 3.3% mark in two separate starts. That’s really not that big a difference from earlier in the season though, as he had only posted a double digit SwStk% in five of 14 starts, but had never posted marks below 5%.

We find a change in pitch mix over the last 30 days, but once again, a change you would expect to result in a higher SwStk%, not a lower mark. He has thrown his sinker less frequently, and upped his usage of his changeup and slider. The velocity on all three pitches is down slightly over the last 30 days, but not enough to raise any red flags.

If we look back at his career, perhaps 2021 was simply the outlier and he’s just not a big swing and miss guy. He makes up for it by consistently generating a strong rate of called strikes, which is currently sitting at a career high this year. It has allowed him to enjoy a strikeout rate rebound despite the drop in SwStk%. I’m still not confident the called strike rate will remain this high, which means that without a rebound in SwStk%, his strikeout rate is likely to drop. He’s still got a strong overall skill set though given the elite GB%, so I wouldn’t consider him a guy owners should look to sell.

Justin Verlander | 9%

I was 100% sure that when Verlander signed with the Mets, this year was going to represent the beginning of the end. Maybe it’s a faulty memory or maybe the facts agree, but it seems like historically the Mets were really good at signing aging veterans after a peak season and immediately experiencing the player’s decline phase.

Verlander’s strikeout rate is at its lowest since 2014, his walk rate highest since 2017, SIERA its highest ever, and ERA its highest since 2014. His full season SwStk% sits at just 9.4%, its lowest since 2014, while his CSW% is his lowest since 2008. This is not the Verlander we have become accustomed to seeing.

Amazingly, his 9% last 30 day SwStk% isn’t actually that much worse than his 9.7% mark earlier in the season. It just stood out to me on the leaderboard because we’re not used to seeing Verlander in single digits over any period of time.

His pitch mix has changed slightly over these last 30 days, as he has slightly reduced his four-seam and slider usage, while bumping up his changeup and curveball. He has rarely thrown his changeup this year, but it actually sports the highest SwStk% of his four pitches, just higher than his slider, which has generated its lowest SwStk% since 2014. So the pitch mix change recently shouldn’t have affected his SwStk% on its own.

His four-seam velocity has remained stable, but oddly he has thrown both his slider and changeup less hard. I wonder if that has resulted in a lower whiff rate. Overall, his pitch mix is near identical to recent years and he has only lost a minor amount of velocity. So nothing there explains why he has lost so many whiffs and strikeouts. He’s a tough one, because on the one hand, his SIERA overperformance suggests a sell high before his results get worse. But on the other hand, will his strikeout rate rebound, at least partially, like the projections think, offset any luck regression? I wish my crystal ball was more effective.