2023 Review: Pitcher ERA vs xERA

Last week, I reviewed the hitters with the largest differences between their actual wOBA and their Statcast calculated xwOBA. Unlike wOBA that’s typically not a fantasy category and has an indirect effect on fantasy value, ERA is almost always a fantasy category. So it’s pretty clear why it’s important to compare it with Statcast’s xERA equation.

Identifying the starting pitchers who both underperformed and overperformed their xERA marks might help you recognize pitcher projections that might be too optimistic or pessimistic, if your source isn’t incorporating Statcast data, and/or weak at forecasting the luck metric trio (BABIP, HR/FB, LOB%) based on historical data. If you’re manually projecting players yourself, you might want to weigh the pitcher’s actual results less heavily, and rely more on how that pitcher was expected to perform given the underlying drivers of the xERA calculation.

Before diving in, it’s important to remember that no equation is perfect. There will always both be outliers based on randomness or player skills that are difficult or even impossible to quantify that would help explain any disparity between ERA and xERA. Therefore, it also helps to review a hitter’s ERA-xERA difference history to identify any patterns. With those caveats out of the way, let’s begin by reviewing the starting pitchers (with at least 120 IP last year) that underperformed their xERA marks the most. I also added Steamer’s 2024 ERA projection.

Joe Ryan is the first fantasy relevant name on this list. He was superb over the first two months, posting sub-3.00 ERA marks, but the wheels fell off the rest of the way, as his ERA skyrocketed in June and then kept climbing the next two months, before dropping a bit in September. His skills were similar during each half, so what was the difference? A .275 BABIP in the first half, following by an inflated .366 in the second half. His HR/FB rate also nearly doubled during the second half, acting as a double whammy. As an extreme flyball guy, it’s surprising to see him struggle with BABIP and end the season with a mark over .300 and worse than the league average.

But if we look past the luck metrics, we find a pitcher who pumped up his strikeout and reduced his walk rate, all the while maintaining the velocity bump he enjoyed in 2022 compared to his 2021 debut. Do be aware that his xERA this season was almost identical to his 2022, the luck metrics merely moved in the wrong direction. There’s a good chance he’s severely undervalued this season in your league, and given his SIERA and xERA history, even Steamer might be underprojecting him.

I’ve never been a fan of Lance Lynn, as he has routinely overperformed his SIERA and used to throw some sort of fastball at least 70% of the time. However, his xERA marks validated his results much better than SIERA did, so it’s clear he was doing something unaccounted for in the more simple SIERA equation. But man, I didn’t think he’d post results this bad in 2023! The BABIP here was normal, but his HR/FB rate surged to a career worst, by a significant margin. It was nearly double his career average. All those dingers allowed pushed down his LOB% to a career low as well, only the second time it’s been below 70%. I’m still not a huge fan, but St. Louis is a fantastic landing spot given their pitcher friendly home park. He might be a good cheap buy this year for a change.

Hunter Brown has nearly all the skills I look for in a pitcher. The only thing I could really see him improve upon is his control, but a walk rate in the 8% to 9% range is perfectly acceptable given his strikeout ability and heavy ground ball tendency. Statcast’s xERA wasn’t as much of a fan of his profile this season than SIERA was, but both suggests he endured lots of bad luck. A .330 BABIP is almost guaranteed to come down, while his absurd 21% HR/FB rate is as locky as locks get to improve as well. Both marks improving should push his LOB% back above 70%. I’m unimpressed with his SwStk%, but he’s struck out batters throughout his entire professional career, so I doubt his strikeout rate gets any worse than the low-to-mid 20% range. After a disappointing 5.09 ERA, he may well end up a steal, though if your leaguemates are using Steamer projections, perhaps not!

Yu Darvish just posted his highest ERA during a 100+ IP season and even his skills took a hit, with his highest xERA and SIERA as well. Perhaps his elbow was hampering his performance all season, an injury that ultimately ended his season early. This is only the second time he’s posted a BABIP over .300, while his LOB% was a career low. At age 37, it’s difficult to predict how the rest and rehab route will affect him, but obviously we all figure he’ll post better results this season. Is he being discounted enough to be worth speculating on? That’s always the key question.

I had to go down enough on this list to ensure I included Spencer Strider. It’s so nutty that a pitcher with his skill set just posted a 3.86 ERA, which was exactly a full run higher than his SIERA, though a bit less so compared to his xERA. Like Ryan above, it’s surprising to see him post an inflated BABIP despite being a fly ball pitcher. Perhaps he deserved some of it, which could explain the discrepancy between his xERA and SIERA. I’m curious if he’ll be discounted at all due to the disappointing ERA or if the majority of fantasy owners are just looking at the monstrous 36.8% strikeout rate and figure his ERA will rebound.

Let’s now move on to the overperformers.

It’s not often you post the second lowest ERA over a 100+ IP season, along with the third highest xERA, but that’s exactly what Blake Snell did last year. His strikeout rate was normal, but this time his control deserted him, as he posted his highest walk rate ever. That didn’t matter though because he stranded 86.7% of baserunners! Oh, and he also posted the lowest BABIP of his career, by a significant margin. Nothing here suggests he’s any better a pitcher than he has been in the past.

Though it was nice to see him record 180 innings, as he hadn’t even reached 130 since 2018, the last time he reached 180 innings. So perhaps his fantasy cost rises compared to his cost heading into 2023 given increased confidence in pitching a full season now, but it shouldn’t rise based on his projections, as his results were seemingly heavily influenced by good fortune. Obviously, his projection will depend on which team he signs with, though given his profile, I don’t think that’s going to matter a whole lot. I think he’ll be overvalued this year, though don’t actually dislike him. Heck, I like any pitcher capable of posting mid-teen SwStk% marks!

Clayton Kershaw has been both amazing in his career, and overperformed his xERA most seasons as well. That’s what the outliers typically do, as equations aren’t built for the Kershaws of the world! After undergoing left shoulder surgery in early November, he’s not expected back until the second half of this season. It’s anyone’s guess how he’ll pitch given his advanced age. Also note he’ coming off his highest ever xERA, and highest SIERA since…2009.

Talk about overperforming your xERA, Wade Miley has now done it by a significant margin each season since 2018 (excluding 2020’s tiny sample size). With a poor strikeout rate, he must continue working his magic to deliver any potential for fantasy value. It’s not a risk I’ll ever be willing to take.

J.P. France seemingly had a solid rookie campaign for the Astros, but his strikeout rate tumbled compared to his minor league days, as he simply couldn’t carry over his whiff skills. However, seemingly a small amount of good fortune across the luck metrics, and perhaps good sequencing, allowed him to overperform both his xERA and SIERA by over a full run. I would imagine his strikeout rate improves, perhaps significantly, so his ERA isn’t going to jump toward 5.00. But I’m guessing he’ll be extremely overvalued given his rookie results.

I loved Josiah Gray as a sleeper heading into the 2022 season, as he was coming off a 14.1% SwStk%, so it figures that after jumping off the hype train, he lucks his way into his first sub-4.00 ERA. This, despite his strikeout rate plummeting thanks to a decline in fastball velocity, an increased walk rate to the highest of his short career, and a continued extreme fly ball tendency. He actually took a step back this season, but might get drafted like a former top prospect on the verge of a breakout. I’m not touching him.

Michael Wacha has overperformed his xERA for most of his career, which he truly has needed to do considering he’s just twice posted a sub-4.00 xERA. He actually overperformed this past season by a lesser margin than in 2022! Having signed with the Royals, he finds himself in a good spot to again overperformed his underlying skills. That means he’s unlikely to regress all the way to his expected ERA metrics and is still worthwhile in deep leagues. He’ll be even cheaper if your leaguemates use Steamer, as the system has likely been very wrong about him pretty often! Just be aware that his fastball velocity hit a career worst, though he was still able to post the second highest SwStk% in a season of at least 100 innings. He’s too risky for me, unless he’s valued like a mid-4.00 ERA guy, which is unlikely.