Szymborski’s 2021 Bust Candidates: Pitchers

Last Wednesday, I looked at some of the hitters who cause me the greatest worry as we approach the start of the 2021 season. Today, this year’s booms-and-busts pieces finish up with the pitchers I’m most grumpy about. Like the hitters, these “busts” represent a combination of players who I think will fall significantly short of their 2020 stats, fail to meet their 2021 projections, or have some troubling flaw that gets me wondering. Only one pitcher is on this list due to injury; given pitcher injury rates, every pitcher has a disturbingly high bust potential stemming from the likelihood that they might make an unfortunate appearance on the 60-day Injured List.

Corey Kluber, New York Yankees

I know, ZiPS isn’t super concernced about Kluber, forecasting a solid 3.87 ERA and 4.12 FIP for the right-hander. But after two years of injuries, I’m far more bearish on him than the projections are. It’s good that the injuries didn’t involve anything elbow-related and that his torn teres major muscle isn’t connected to the rotator cuff. Still, one thing I’ve found in pitcher projections is that the volatility after two consecutive lost seasons is massive. Kluber may be fine, but the downside scenarios are so scary that I’m not sure he’s a good fit for the Yankees, who have a lot of risky pitchers after Gerrit Cole. Given how plentiful the worst-case scenarios are, I sadly have to put Kluber as a serious bust candidate.

Patrick Corbin, Washington Nationals

My colleague Jeff Zimmerman is worried about Patrick Corbin and I am too. His velocity was down in 2020, and on a per-pitch basis, his slider was less than half as effective than his career average and even further below where it was in his peak years. Compared to 2018, his best season and the reason he was highly sought after in free agency that winter, a full third of the pitches batters were whiffing against turned into contact in 2020. In the past, he’s had problems with his effectiveness when his fastball’s command has been off, something he’s well aware of:

“Everyone wants to talk about my slider, and how effective it is, but it really can’t be without fastball command,” Corbin said in San Diego, a day after coughing up a four-run lead in a loss to the Padres. “It starts with my fastball, even if the slider is the pitch I want to get to. I’m just not locating right now.”

To verify Jeff’s theory about his fastball’s velocity (rather than his command of it) also having a deleterious effect on Corbin’s slider’s performance, I went back through game logs for the last three years and looked at all his sliders that came after hard pitches. When the sliders came after pitches over 90 mph, they had a swing-and-miss rate closer to the over-50% rates he posted in 2018 and ’19 than the 39% whiff/swing he posted rate in ’20. So I’m worried, too.

Jon Lester, Washington Nationals

I was fretting about Lester’s outlook well before any concerns popped up about his thyroid, which was recently removed. Lester has lost about a third of his swinging strikes since 2017, and he hasn’t been compensating by inducing softer contact. In fact, it’s just the opposite: his Statcast hard-hit percentage was his worst so far in 2020, bordering on 40%. His K/9 dropping to six was no fluke. I could see Lester fulfilling the old crafty lefty stereotype and surviving with a sub-90 mph fastball, but not until I see him throw a more effective curveball than he did in 2020 or showing a better aptitude for changing speeds. The curve was particularly ineffective last year, with batters not even bothering to swing at it a quarter of the time and slugging .588 when they did. Expectations are limited due to his one-year, $5 million contract, and I’m not sure he’ll even meet those.

Martín Pérez, Boston Red Sox

Martín Pérez had a nice run back in early 2019 when his cutter was shiny and new. But after he started losing velocity — he was throwing 96 mph regularly in early 2019 — and resorted to nibbling around the zone more often, the strikeouts faded, and the runs piled up, enough that he was barely in Minnesota’s plans by the end of the season. 2020 wasn’t any better of a story for Pérez, as he lost more velocity. And while he was nibbling, batters were taking grizzly chomps; he remained difficult to hit hard, but he still became very hittable. Pérez ranked last in the majors among ERA qualifiers with the lowest swing rate for out-of-zone pitches, so he’s likely going to continue to allow a multitude of balls in play. If he doesn’t have a .266 BABIP as he did in 2020 (his career mark is .310), he might be out of a job before we get to the All-Star break.

Marco Gonzales, Seattle Mariners and Johnny Cueto, San Francisco Giants

Both players jump out to me for similar reasons: ZiPS sees this pair as two of the biggest overachievers in terms of 2020 strikeout rate. For Gonzales, ZiPS thinks he “should have” racked up 13 fewer strikeouts than his actual 64 based on the plate discipline stats of opposing batters. For Cueto, ZiPS similarly takes out the scalpel, slashing his 56 strikeouts to 40. Now, neither pitcher is a hard tosser, but they also have no history of over-performing the zSO stats that ZiPS calculates.

zSO vs. Actual Strikeouts (min. 50 IP)
Season Player SO% zSO Overperformance
2008 Johnny Cueto 20.5% 23.8% -3.2%
2009 Johnny Cueto 17.8% 15.1% 2.7%
2010 Johnny Cueto 17.7% 19.3% -1.6%
2011 Johnny Cueto 16.5% 14.7% 1.7%
2012 Johnny Cueto 19.1% 18.0% 1.1%
2013 Johnny Cueto 21.1% 22.2% -1.1%
2014 Johnny Cueto 25.2% 23.2% 2.0%
2015 Johnny Cueto 23.3% 21.9% 1.3%
2015 Johnny Cueto 16.0% 17.2% -1.2%
2016 Johnny Cueto 22.5% 20.3% 2.2%
2017 Johnny Cueto 21.0% 20.6% 0.3%
2018 Johnny Cueto 17.8% 17.6% 0.1%
2020 Johnny Cueto 20.2% 14.6% 5.6%
Season Player SO% zSO Overperformance
2018 Marco Gonzales 21.1% 21.0% 0.1%
2019 Marco Gonzales 17.0% 16.9% 0.1%
2020 Marco Gonzales 23.1% 18.4% 4.7%

There are other pitchers who over-performed their actual strikeout rates, such as Shane Bieber, Trevor Bauer, and Rick Porcello. However, pitchers like Bieber and Bauer have much more room to lose some strikeouts, and if anyone is rating Porcello highly, it’s the first I’ve heard of it. Cueto and Gonzales have different outlooks: I think Gonzales will go back to being a dependable No. 3 starter while Cueto risks falling out of the Giants’ rotation by the end of the season. After years of injury setbacks, I’ll admit that I was hoping we’d get one final season of Johnny Cueto dominating with his filthy change, but I’m not sanguine about that happening.

Rich Hill, Tampa Bay Rays

There’s risk in being pessimistic about a Rays pitcher, given the team’s knack for squeezing good performances seemingly out of nowhere. But when a pitcher loses four strikeouts per nine in a single season, I’m going to furrow my brow even when that pitcher isn’t on the wrong side of 40. And even worse, there was no sign that Hill’s strikeout rate was the source of some bad fortune; ZiPS thinks that the drop-off should have even been worse given his swinging strike rate. Surveying the pitchers who’ve suddenly lost at least a third of their swinging strikes in a single season, we find a graveyard for many careers, including those of Rich Harden, Adam Eaton, Brad Penny, Mark Redman, Phil Hughes, and so on. Hill hasn’t entered the danger zone; he’s entered the Lovecraftian horror zone.

Dustin May, Los Angeles Dodgers

I’m quite optimistic about May over the long haul, but just speaking about 2021, I think he’s well behind Tony Gonsolin as a pitcher, rather than as just a thrower. There’s still too much Nathan Eovaldi to wring out of him, by which I mean early-career Eovaldi, when there was a huge disconnect between the explosiveness of his fastball and his ability to punch out batters. With the minor league season delayed, May ought to start the year in the Dodgers bullpen, but I think he could still use some time at Triple-A. A guy who can hit 100 mph on the radar gun ought to have a better two-strike strikeout percentage with his fastball (13.5%) than Merrill Kelly (13.8%) or Zack Greinke (17.0%) has with theirs. Again, May will be fine eventually, but there’s danger in expecting too much, too quickly.

Dan Szymborski is a senior writer for FanGraphs and the developer of the ZiPS projection system. He was a writer for from 2010-2018, a regular guest on a number of radio shows and podcasts, and a voting BBWAA member. He also maintains a terrible Twitter account at @DSzymborski.

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Brian Reinhart

Interesting to note that the Nationals seem aware of their pitcher pitfalls. The Athletic just reported that Corbin is learning a cutter from Max Scherzer which is about 5mph faster than his classic slider. And personally I’m hopeful that a lot of Lester’s stamina and strength issues the last couple years can be attributed to the thyroid problem.

Still, they’re both racing Father Time, as are Scherzer and Strasburg, for that matter.