Last 30 Day Starting Pitcher SIERA Leaders – 6/23/21

Pitchers can change rapidly. Whether it’s changing their mix pitch, gaining or losing velocity, adjusting their mechanics, or something else, a pitcher we see today isn’t necessarily the same version we were expected during draft season. So it’s important to always monitor their underlying skills to see if the results suggest a new pitcher has arrived, whether better or worse. With that in mind, let’s dive into the last 30 day SIERA leaders. Are there any surprises among the crowd?

I’ll mostly keep my comments to the surprising names, rather than discuss each one.

Jacob deGrom…there are simply no words.

Zack Wheeler’s SIERA has sat above 4.00 in four of his six seasons. Suddenly, he has transformed himself into one of the best pitchers in baseball and a super elite over the past 30 days. His fastball velocity has risen for a fourth straight season to another new career high, while he’s throwing his slider the most he ever has. He has thrown his curveball a bit more in recent games as well, but nothing over the last 30 days specifically points to the massive performance spike. That said, with the increased velocity and a solid assortment of secondary pitches, he looks like he should remain one of the better pitchers in baseball, though obviously I wouldn’t go expecting a continued sub-3.00 ERA or SIERA.

Carlos Rodon proves that no matter how much research you do into historical performance, there’s sometimes just no way to project breakout starting pitcher performances. Rodon has undergone both shoulder surgery and Tommy John surgery, in 2017 and 2019 and then missed time with shoulder soreness last year after returning from the latter procedure. With an ERA below 4.00 just once (during his 2015 debut) and a SIERA below 4.00 just once (his sophomore 2016 season), you would be forgiven if you completely ignored him during draft season. Sure, he pitched a strong 13.2 Spring innings with 16 strikeouts and just one walk, but c’mon, it’s spring training and a ridiculously tiny sample size. Anyhow, his fastball velocity is up a whole 2.9 MPH versus last year and 1.5 MPH from his 2016 peak. It seems those surgeries have actually made him better! While there’s always the chance his previous control issues return, I see no reason to expect dramatic skills regression for as long as he maintains this elevated velocity. Of course, it’s hard to sustain a mid-30% strikeout rate, but this is most certainly a new Rodon and it’s wayyyyy better than the old version, even if his strikeout rate drops back a bit.

Oh look, Chris Paddack fixed his HR/FB rate problem! Or perhaps maybe last season’s 25% mark was just some really poor fortune magnified over a small sample size. His pitch mix and velocity haven’t changed much over the last 30 days, he’s simply getting better results, including two straight games with a SwStk% above 20%, which is insane. I see no reason why you shouldn’t expect a sub-4.00 ERA the rest of the way, as his LOB% should rebound back above 70%.

Alex Cobb, strikeout pitcher?! Cobb has historically been an extreme ground ball pitcher with an above average walk rate and below average strikeout rate. It’s a skill set more appealing in real baseball given the lack of strikeouts. This year, his strikeout rate has skyrocketed, while his SwStk% has surged to a career best, above 11% for the first time and just the third time in double digits. He is throwing his splitter more than ever before, though its usage has actually dropped over his last four games. For the season, his splitter’s SwStk% is above 20% again, but he’s finally getting a double digit SwStk% from his curveball, which he’s done just once, back in 2016. I don’t think this adds up to the elevated strikeout rate he currently holds, but he is deserving a better strikeout rate than his career mark, for sure. When combined with his career best 60.6% grounder rate and better than average walk rate, you’re left with a superb SIERA, making him a prime target to acquire given his significantly higher ERA.

Look at what a little bit of control could do for Robbie Ray! It hasn’t just been the control. His fastball velocity has also not only rebounded, but now sits at a career best. He has also upped the usage of his slider at the expense of his curveball over his last five starts, but with similar SwStk% marks, that switch probably didn’t have a huge impact.

Look at Austin Gomber with that tiny walk rate! Too bad he just landed on the IL.

Tyler Mahle’s fastball velocity has kept rising and this year he’s throwing his cutter even more, though the pitch’s SwStk% is well down from last year. His splitter has been his best whiff pitch, but he throws it least of his three offerings.

Pablo Lopez has taken it up a notch the past 30 days, primarily thanks to the minuscule walk rate. That won’t last though so look to his season SIERA of 3.67 to get an idea of what you might get from him over the rest of the way.

Taijuan Walker with strikeouts?! Finally! Even with mid-90s heat, Walker was never able to post even a 23% strikeout rate. The problem has been that none of his pitches were actually any good at generating swings and misses. This year, not much has changed, though his four-seamer’s SwStk% now sits at 12.4%. That’s really good when it’s your primary pitch, but it’s a big jump from the high single digits he typically lived in. His pitch mix has really varied from game to game and there hasn’t been much change over the last 30 days. His velocity isn’t up either, so I’m not sure what’s driving the sudden strikeout rate outburst. I still feel like he simply doesn’t have good enough pitches to sustain a high strikeout rate, as it’s difficult when all your pitches sit in the low double digit and high single digit SwStk% range.

Jose Urquidy’s strikeouts are back after a small sample decline last year. His changeup is his best whiff pitch, but he’s actually thrown it less often in three of his last four games than he has during the season on the whole. He also hasn’t gained any velocity. So this appears to be another pitcher who its difficult to identify the driving force of the increased strikeout rate.

Framber Valdez is why I love groundball pitchers. His other underlying skill rates are fine, but it’s the 71.1% groundball rate that makes him so good.

Man, I love ultimately being proven right about a pitcher after I forgot about him. I’ve been a fan of Patrick Sandoval since 2019, but with no starting role, I lost interest. He owns an incredible changeup/slider combination and generates a high rate of groundballs. He should remain a mixed league asset moving forward.

Shane McClanahan has been strong during his MLB debut and that 17.6% SwStk% is pretty amazing. So far two pitches of his, his slider and curveball, have generated a SwStk% above 20%, while his changeup is still in the mid-teens and his four-seamer above average for the pitch type. Who knows how long hitters will find making contact with his stuff impossible, but he’s been one heck of a pitcher so far.