Discussing Five Last 30 Day Starting Pitcher K% Laggards

Yesterday, I discussed five starting pitchers who appear inside the top 20 in strikeout rate over the last 30 days. These weren’t necessarily the leaders, but interesting names worth a deeper dive. Let’s now flip to the other side and discuss five pitchers who appear near the bottom of the strikeout rate leaderboard over the last 30 days.

Kolby Allard | TEX | 13.6% K%

Allard joined the Rangers rotation toward the end of May, after posting strong skills as a reliever, including a 26.7% strikeout rate and 3.42 SIERA. But as is often the case when a pitcher transitions from the bullpen to the rotation, serious skills degradation has occurred. As a starter this year, he has posted just a 17.4% strikeout rate and 4.70 SIERA, pushing him from a positive contributor in AL-Only leagues as a reliever to free agent material as a starter.

In the last 30 days, things have gotten even worse as his strikeout rate has plummeted even further to just 13.6%. That has coincided with another spike in SIERA all the way to 5.40. Not surprisingly, his fastball velocity is a bit lower than when he was pitching in relief, but not dramatically so. When comparing his last 30 days in the rotation to his earlier time in the rotation, his pitch mix has barely changed, while his fastball velocity is down a mere three miles per hour. So it doesn’t appear that a different in stuff is the culprit for the huge drop in strikeout rate.

He doesn’t generate a high rate of swinging strikes, so it’s possible he’s just hit a dry spell in terms of called and/or foul strikes. Obviously, pitchers aren’t going to post the same strikeout rate during every single 30 day period and sometimes the explanation is no more than randomness. So I would expect his strikeout rate to rebound, at least toward his previous mark as a starter. It still wouldn’t make him worth rostering though.

Kyle Gibson | PHI | 14.5% K%

Gibson owned one of the largest ERA-SIERA gaps among starting pitchers when he was traded to the Phillies at the end of July. Unsurprisingly, his luck has begun to fade in Philadelphia, as his ERA has spiked above 4.00 and sits a lot closer to his SIERA.

Normally, a pitcher moving from the AL to the NL will enjoy a strikeout rate boost as they no longer have to face the DH, unless in interleague games. That hasn’t happened for Gibson, as his strikeout rate has actually decline precipitously. At least he has induced a high rate of ground balls, so he’s able to erase some of those baserunners via the double play, but it still kills his fantasy value.

Over the last 30 days, Gibson has upped the usage of his cutter, at the expense of his sinker, changeup, and curveball. While the cutter generates more swinging strikes than his sinker, the latter two pitches have generated the second and third highest SwStk% marks for him. So it’s not too surprising that throwing them less frequently would result in fewer strikeouts. In addition, his sinker velocity has decline 0.8 MPH, which is meaningful, especially as velocities are typically higher during the summer than earlier in the year.

Gibson was a first half wonder thanks to stupendous fortune, rather than any improvement in underlying skills. After a terrible July, the magic returned in August. Don’t feel silly if you’re considering benching, or even dropping, him as the skills have never been there — he’s never posted a sub-4.00 SIERA and just twice has his ERA settled below 4.00.

Marco Gonzales | SEA | 16.1% K%

Gonzales’ strikeout rate spiked last year over a small sample thanks to a career high called strike rate. That hasn’t lasted though and his season mark has dropped right back toward his career mark. But he’s struggled on the strikeout rate front over the last 30 days, even though it hasn’t affected his run prevention, thanks to good fortune resulting in a sizeable gap between his ERA (3.06) and SIERA (5.05).

Over the last 30 days, Gonzales has oddly upped the usage of his four-seamer at the expense of his curveball, which has generated the second highest SwStk% of his repertoire this year, and a significantly higher mark than his fastball. His velocity hasn’t changed at all, so it seems pretty clear that a simple change in mix could be behind most of the strikeout rate drop. I’m not sure why he would have changed his mix in such a way, as his four-seamer is nothing special on the whiff-inducing front.

Gonzales has once again continued his SIERA outperformance for the season, posting another suppressed BABIP, and notching a career high LOB%, versus essentially a league average career mark. I’m not sure that 629 innings is enough to anoint him a consistent SIERA beater, but he’s the type that will never end up on any of my fantasy teams.

Chris Flexen 플렉센 | SEA | 16.3% K%

At the end of June, I engaged in a deep dive on Flexen, as his last five starts leading up to that post saw a version of him that finally included a league averageish strikeout rate. Sadly for those excited about the surge and rostered him, his strikeout rate is back down again.

His pitch mix has changed slightly, as he has thrown more four-seamers at the expense of his cutter, while slightly reducing his changeup usage in favor of his curveball. For the season, both his four-seamer and cutter are below average at inducing whiffs, so the change there isn’t going to have a dramatic effect on his strikeout rate. His changeup has been better at generating whiffs than his curveball, but the difference in usage is minimal. From a strictly pitch mix perspective, there doesn’t seem to be an obvious answer.

Flexen’s fastball and cutter velocity have also remained stable, so we have no answers there. But if you recall from my previous post dissecting his strikeout rate spike from late-May to mid-June, you will remember that his velocity did spike at the time to consistently above 93 MPH. It’s not a huge increase compared to his 92.8 MPH last 30 day and previous period velocity, but maybe given his pitch quality, it makes a bigger difference than most.

Depending on how he finishes the season, he’s an obvious bust candidate in 2022 if owners are buying a mid-3.00 ERA.

Carlos Hernandez | KCR | 17.5% K%

Hernandez entered the season as the Royals’ 17th best prospect as a future middle reliever. He did open the season in the bullpen, but was used for multiple innings several times, and then moved into the rotation on July 18. As a reliever, he posted a 30% strikeout rate, but had no idea where the ball was going, as evidenced by his inflated 15% walk rate. Despite the high walk rate, he still managed to post an acceptable 4.10 SIERA, though that’s not good enough to make your fantasy team in a relief role.

As a starter, his skills have completely changed. His strikeout rate has dropped to just 20.4%, but his walk rate has been nearly cut in half to 8.4%. That’s more like it! His SIERA, though, jumped anyway to 4.58. If we compare his last 30 days to his previous starts in the rotation, we find both his strikeout and walk rates initially dropped, but have dropped significantly more over his last 30 days. His skills are now completely unrecognizable as coming from Hernandez. Interestingly, his SIERA hasn’t budged.

So how has his pitch mix and velocity changed since joining the rotation? He has thrown his fastball a bit more often at the expense of his curveball. Normally, you would expect that to reduce a pitcher’s strikeout rate, but the SwStk% on those pitches this year are nearly identical. Initially upon moving to the rotation, he slightly upped his splitter usage as well, but that’s come back down to where he was as a reliever. His splitter’s SwStk% is the same as his four-seamer and curveball. The final change is over the last 30 days, he has increased the use of his slider, which has easily been his best whiff pitch.

As you might expect, his fastball velocity has declined just over a mile per hour over his last 30 days versus his time as a reliever. Since his pitch mix wasn’t enough to explain the drop in strikeout rate, perhaps he needed that extra velocity to drive all those strikeouts. You wouldn’t think a drop of just one mile per hour would make such a big difference in strikeout rate, but depending on the pitcher’s command and pitch mix/quality, perhaps it could.

I have no idea what to expect from Hernandez moving forward, but obviously this low strikeout version isn’t very valuable in fantasy leagues.