Can Chris Flexen Stave Off The Regression Monster?

[RandallPnkFloyd]

Image courtesy of © Patrick Gorski-Imagn Images

Despite just about everything that unfolded at Wrigley Field over the weekend, the Chicago Cubs' bullpen had been one of the league's best since the start of May. Even including the trio of rough outings for the collective against Seattle, the relief corps features the best ERA (2.71), the fourth-best FIP (3.48), and the fourth-best walk rate (7.7 percent) in Major League Baseball since May 1st. 

There are, of course, a handful of reasons for the increased success of the 'pen (and how "real" various runs are for various arms). But, Chris Flexen has certainly played a role in such an ascent for a group which Craig Counsell struggled to piece together innings in April. Through a baker's dozen worth of outings for the Cubs, Flexen has been nearly flawless, at least to this point. 

Across those 13 appearances, Flexen has posted a sterling 0.78 ERA. Within the broader context of the Cubs' bullpen, Flexen features both the team's lowest ERA and lowest WHIP (0.87) among those with at least 10 innings. Sunday's tough one was the first time he'd allowed an earned run to score, which becomes even more impressive when you consider that eight of his appearances have been of the multi-inning variety. That includes the notable outing last Thursday, in which Flexen tossed three clean innings to allow the Cubs a chance in what ultimately resulted in an 8-7 loss following a brutal Jameson Taillon start.

Prior to Sunday, Flexen's success had me wondering if the Cubs should give him a little bit of a run as a starter until reinforcements arrived in the shape of health or trade. After all, this was a guy that pieced together at least reasonable results (4.80 FIP) for a historically bad Chicago White Sox team in 2024. "If he's capable of handing multi-inning stretches in relief, perhaps it would behoove Counsell to give him a start in favor of Colin Rea or Ben Brown considering their respective struggles of late," was a thought that crossed my mind more than a couple of times in the last couple of weeks. 

Until I looked deeper. 

Not only would it be ill-advised to deploy Flexen out of the gate, it's possible that regression is nigh for the reliever, if expected outcomes are to be believed. His ERA looks quite good, yes. His WHIP, too. But, under the surface, this is a guy who, at first blush, appears to take a step back as his 2025 volume increases. 

The hallmarks are there. Flexen's BABIP against is .188. He's working with a 91.4 percent strand rate. His HR/FB ratio is 4.8 percent. Flexen's career marks in each category? .304, 71.8, and 11.4, respectively. While the career totals are at least something of an oversimplification given his condensed role with the Cubs, the expected stats still aren't as favorable as his actual outcomes. He's at a 3.19 xERA, a .244 xBA, and a .350 xSLG. We likely wouldn't consider those bad as true outcomes, but they do speak to how much he's been able to outperform his peripherals. 

And that's due to the fact that his stuff just isn't overpowering enough to sustain such a stretch. It's a 20th percentile fastball in terms of velocity with a 15.3 percent strikeout rate that sits ahead of only Nate Pearson among the Cubs' bullpen regulars. His "best" pitch by Stuff+ is his changeup (94), which he only throws 2.1 percent of the time. A contact-oriented, primarily multi-inning reliever is always going to be the first guy to go in the regression game. Volatility is the nature of relief, after all.

What Flexen does have working in his favor, at least, is his ability to minimize quality contact. And that works as a starting point for why regression might not be around the next corner, but maybe the one after that. His 3.1 Barrel% is easily the best of his career, along with a 35.4 percent Hard-Hit rate that serves as his best since 2017. When you work those in with a solid 46.2 groundball rate, it's no wonder Flexen has been able to string together success in the way he has. It's that ability to work around the barrel that could allow Flexen to maintain this performance longer than he has any right to.

Flexen's three primary pitches this year have been his fastball, his cutter, and his curveball: 

The first two pitches represent the norm for his career. But the introduction of the curveball as more of a fixture in his arsenal appears to be what is making the difference. Opposing hitters have mustered a Hard-Hit% of just 22.2 against the hook and have yet to barrel one off Flexen. At 44.4 percent, it's also where he's garnering the highest rate of groundballs. So, that uptick in usage appears to be making the difference for him.

What important to note about the offering is that it's not a strikeout pitch, but a driver of Flexen's success in 2025. He's dropping that pitch into the middle of the zone horizontally while varying the vertical: 

Subsequently, he's getting a fair bit of chase (30.4 percent), a fair bit of whiff (29.6), and a terrific bit of both (57.1 chase & miss rate). Factor in the groundballs, and it starts to become valid thinking that Flexen could stave off regression quite a while longer when you add in a near 20-point gap below his fastball & cutter in Hard-Hit%. Plus, he has a manager deploying him the correct spots and in possession of the knowledge as to when his outings should carry into a second or third inning.

The regression monster comes for us all eventually. But, thanks to the curveball, Chris Flexen might have the silver bullet to keep it at bay a while longer.

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