Top 20 Starting Pitcher SIERA Leaders

Even though we are about halfway through the season, the league leader in innings pitched sits at just 40.2 innings. That’s far too small a sample size to find much meaning in traditional surface statistics such as ERA and WHIP (plus LD%, HR/FB, BABIP, etc). The results that feed into ERA take significantly longer to stabilize, so it makes more sense to focus on the underlying skills that pitchers have more control over. Luckily, we have a metric that takes all those underlying skills, throws them into a blender, and spits out a skills-based ERA. Of course, I’m describing SIERA, and it’s what I exclusively look at early in the season to forecast future performance, as it’s far better than ERA itself. So with that said, let’s take a gander at the top 20 qualified starting pitchers in SIERA and discuss any surprises.

Shane Bieber is the poster child for ignoring results like BABIP that take a long time to stabilize, and instead focusing on the underlying skills. In his 2018 debut, he dramatically underperformed his SIERA, primarily because of a .356 BABIP. The justification was that his “fastball was too hittable”, which automatically means that .356 BABIP was deserved, I guess. Did he fix that hittable fastball overnight? Because his BABIP in 2019 was a league average .296 and this year, it’s sitting at just .284. While not every pitcher in baseball is good enough to post a BABIP near the league average, they get weeded out pretty quickly, and you have to assume if you’re good enough to post a near 20% K%-BB%, you’re better than a .356 BABIP.

Trevor Bauer would make it easier for fantasy owners to project him for the season if he told us ahead of time which version of himself would show up that year. His slightly altered pitch mix and decreased velocity doesn’t exactly explain the surge in skills, so I’m not entirely sure what’s behind the elite early results.

I discussed Kevin Gausman yesterday, and his ranking here is what made me proclaim his breakout was happening. As mentioned in the intro, his inflated LD% is rather meaningless, as it takes a whopping 650 balls in play for that rate to stabilize. Gausman is currently at 84. So while the inflated LD% might explain the high BABIP, it doesn’t mean he deserves all the blame. SIERA is meant to capture what a pitcher can control and based on what he has control over, he has been elite.

Though it’s only been 22.1 innings due to the early COVID-19 outbreak on the Marlins interrupted their season, Pablo Lopez’s skills have surged. The spike in SwStk% and K% appears mostly due to the increased usage of his best pitch, the changeup, which has generated a mid-20% SwStk%. He has also become an extreme ground ball pitcher, so suddenly everything has fallen into place in his first four starts. Will it continue is the most important question.

Thrust in the Astros starting rotation, Framber Valdez has solved his control problems so far, and continues his strong combination of strikeout ability and extreme ground ball tendency. The skill set looks like Dallas Keuchel, so he’ll probably be more valuable in real baseball due to the mediocre strikeout rate, but he should remain a solid asset for as long as his control remains decent.

Dylan Bundy has posted a SIERA just below four before, so this isn’t completely out of nowhere. But this year his K% has spiked, despite a stable SwStk%. Behind the breakout is increased usage of his slider and changeup, at the expense of his weak fastball. Give credit to the Angels for getting him to focus on his best pitches and throw his worst pitch less frequently. Interestingly, his LD% is just below Gausman’s at 25%, yet his BABIP is significantly below the league average, reminding us once again that these metrics jump all over the place over a small sample and should just be ignored.

I was not a fan of Aaron Civale heading into the season, as he was getting sleeper love for his 2.34 ERA, even though his SIERA stood at an ugly 4.74. This season, he has dramatically improved his underlying skills…and his ERA has risen. Yet, his ERA still stands below 3.00 and now SIERA suggests he has actually been a good pitcher, rather than a bad one benefiting from great fortune. He has thrown his curveball and changeup more frequently, which have generated the highest SwStk% marks of all his myriad pitches, but his sinker remains his bugaboo, generating a measly 1.3% SwStk%. I don’t think I’ve ever see a pitch thrown that often with a SwStk% that low! It does generate grounders though, but man, you still need to induce more whiffs or that’s potentially a lot of hits.

Zac Gallen is essentially doing what he did last year during his debut, but with better control, more in line with his minor league days. I still don’t understand why they traded him for a guy who had been striking out over 30% of the time in the minors. It’s not even like a veteran for prospect trade you see in keeper leagues, as Gallen was a rookie himself, but at least already enjoyed success during his short time in the Majors!