Starting Pitcher xERA Underperformers — Jun 23, 2022

I haven’t done a lot of research on Statcast’s xERA metric, but it’s similar to batter xwOBA in that it uses a pitcher’s actual batted balls against to compute what a pitcher’s ERA “should” be. That means for all those who love justifying a pitcher’s low BABIP being the result of allowing soft contact, xERA should theoretically account for this. Now, this doesn’t mean the pitcher will continue to allow the types of batted balls that have resulted in a suppressed or inflated xERA, but it does suggest that what they have already allowed should yield the calculated xERA. So let’s review the pitchers who have most underperformed their xERA marks.

xERA Underperformers
Name K% BB% BABIP LOB% HR/FB ERA xERA Diff
Alex Cobb 27.2% 7.2% 0.381 55.6% 19.2% 5.62 2.23 3.39
Elieser Hernandez 21.6% 6.9% 0.269 69.0% 21.2% 6.75 5.06 1.69
Hunter Greene 30.1% 9.9% 0.260 75.6% 18.3% 5.26 3.67 1.59
Zach Eflin 20.2% 4.9% 0.290 65.9% 11.1% 4.43 2.99 1.44
Dylan Bundy 18.8% 4.3% 0.302 69.0% 13.7% 5.17 3.80 1.37
Tyler Mahle 25.9% 8.9% 0.309 66.8% 8.0% 4.57 3.23 1.34
Austin Gomber 18.0% 7.4% 0.332 57.7% 12.7% 6.43 5.13 1.30
German Marquez 20.1% 7.3% 0.338 61.8% 20.0% 6.16 4.87 1.29
Aaron Ashby 27.5% 10.7% 0.336 70.7% 18.8% 4.25 3.01 1.24

My gosh, Alex Cobb is far and away the xERA underperformance king so far, though it’s come in just over the minimum innings I set of 40. With a career best strikeout rate and GB%, it’s shocking to see how inflated his ERA is. You can thank the trio of inflated BABIP and HR/FB rate, along with a suppressed LOB% for the underperformance. Cobb is not a perennial underperformer either, in fact, he has overperformed every year of his career. Oh, and his sinker has gained nearly two miles per hour of velocity. You might be lucky enough to find him sitting in your free agent pool. He’s a screaming buy.

With a high 90s fastball, Hunter Greene got a lot of sleeper love when he was competing for a rotation spot out of spring training. So far, the skills have been there, including a 30.1% strikeout rate. But an inflated HR/FB rate, combined with an insane 56% FB%, have wreaked havoc on his ERA. Great American Ballpark isn’t exactly the best park to be an extreme fly ball pitcher. That HR/FB rate figures to decline, but the FB% remains scary. He makes for a good buy in keeper leagues, assuming he’s cheap, but I’m a bit hesitant in single season shallow mixed leagues.

It’s hard to believe in Zach Eflin’s xERA, given his mediocre strikeout rate and overall skill set. Plus, while his LOB% is a bit low, his BABIP and HR/FB are fairly normal. It’s clear that based on his batted balls against, Statcast thinks he should have enjoyed better luck, but I wouldn’t expect it to last given his history. However, he has changed up his pitch mix, throwing a cutter now and his curveball significantly more, at the expense of his changeup and slider. That hasn’t made a lick of difference in the underlying skills, but perhaps has led to worse quality contact by opposing batters that should have yielded better results. Still, I’m not buying here.

Dylan Bundy has been an xERA underperformer for the majority of his career, but much of that was because he pitched half his games in a hitter’s paradise in Baltimore. With his fastball velocity down below 90 MPH for the first time, his strikeout rate has plummeted, while his BABIP has jumped to the second highest mark of his career. He could probably do better than a 5.17 ERA, but I have no interest here given the velocity loss leading to fewer strikeouts.

The second highest BABIP and second lowest LOB% of Tyler Mahle’s career has driven his ERA higher, but his xERA is actually the lowest of his career. I’m guessing that HR/FB rate is going to rise, but it should be offset by a drop in BABIP and increase in LOB%. I’m a bit concerned that his FB% has risen, so an increase in HR/FB rate could really up the homers allowed.

I’m never sure how to treat Rockies players when it comes to Statcast metrics, but German Marquez’s SwStk% has plummeted and strikeout rate is at a career low. So unlucky or not with his 6.16 ERA, I’m not interested, even if he does see better results the rest of the way.

Hopefully Aaron Ashby’s injury doesn’t knock him out too long, as I’m really intrigued by his combination of strikeouts and groundballs. A combination of inflated BABIP and HR/FB rate has driven up his ERA and overshadowed an exciting skill set. This is a good opportunity for keeper leaguers to try buying here.





Mike Podhorzer is the 2015 Fantasy Sports Writers Association Baseball Writer of the Year. He produces player projections using his own forecasting system and is the author of the eBook Projecting X 2.0: How to Forecast Baseball Player Performance, which teaches you how to project players yourself. His projections helped him win the inaugural 2013 Tout Wars mixed draft league. Follow Mike on Twitter @MikePodhorzer and contact him via email.

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Werthlessmember
12 days ago

Sometimes this stat can also be “pitching in front of a bad defense” or “pitchers who have struggled executing their pitches out of the stretch.” The former results in poor outs conversion, and the latter can result in low LOB% and what could look like unlucky sequencing of hits.

hmmph3
12 days ago
Reply to  Werthless

For Alex Cobb, it is certainly the former (so far).

si.or.nomember
12 days ago
Reply to  hmmph3

Why do you say certainly? Looking at the xWOBA for pitchers on the Giants, there don’t seem to be any particularly obvious trends there.

Wouldn’t bad defense reflect across all of their pitchers?

Mentholmember
11 days ago
Reply to  si.or.no

I believe hmmph3 is referring to a memorable bad outing this year where the Giants defense just ruined him. (But I’m apparently too old to remember it well.)