Baseball's unluckiest reliever Declan Cronin poised for much better results in 2025

On the surface, Declan Cronin’s 2024 season was nothing to write home about, yet here we are. While Cronin’s 4.35 ERA was third-highest among the 37 MLB relievers to throw at least 70 innings, examining the right-hander through the lens of FIP (fielder independent pitching) paints him as the victim of incredible misfortune.

If we go bigger picture and look at pitchers who threw at least 70 innings out of the bullpen in a single season since the start of the 21st century, Cronin’s gap between his ERA and FIP is the third-highest this millennium. 

“It’s not lost on myself or the pitching staff that a lot of the things that transpired and outings that didn’t go so well were kind of out of my control,” noted Cronin to our Kevin Barral.

What factors contributed to Cronin’s historically lousy luck? The best place to start would be his profile. 

Despite his 6-foot-4, 225-lb build, Cronin doesn’t possess an overpowering fastball, with an average velocity of 93.4 mph placing him in the 38th percentile in that regard. Cronin’s sinking-two-seamer, a pitch he featured 40.6 percent of the time last season, wasn’t a pitch that made its living inducing swing-and-miss as evidenced by a 15.9-percent whiff rate. Opponents had a .340 batting average on the offering—only seven pitchers allowed hits more frequently on their sinker (min. 100 PA ending on the pitch), while only eight had a higher hard-hit rate than his 52.3 percent. 

Of the 35 hits he surrendered on sinkers last year, only four registered as barrels (a ball which leaves the bat at no less than 98 mph and with a launch angle between 26 and 30 degrees). Meanwhile, 14 of Cronin’s hits allowed on sinkers had a negative launch angle, indicating that 40 percent of those hits came on ground balls, a specialty of Cronin’s and the type of contact that major league defenses convert into outs the vast majority of the time. His 57.6 percent groundball rate overall put him in the 95th percentile across baseball. 

Accompanying that elite groundball rate is Cronin’s ability to limit the long ball. He and Kyle Barraclough (2016) are the only pitchers in Marlins history to face at least 300 hitters in a season while allowing fewer than two home runs and also averaging more than a strikeout per inning (9.2 K/9 in Cronin's case).

Cronin, unfortunately, pitched in front of one of the sport’s worst defenses. The Marlins ranked 28th in team defensive efficiency at .681, well below the league average mark of .697. Similarly, they finished 27th in outs above average and 29th in range runs above average. No team made more than Miami’s 117 errors last season.

Some improvement is expected in 2025, but concerns still linger. Xavier Edwards, expected to be the club’s everyday shortstop, graded out as one of the sport’s worst defenders, finishing in the first percentile in OAA while boasting 20th percentile arm. There’s also the Connor Norby of it all. He enters his first full season in the majors tasked with being Miami’s starting third baseman, a position that largely got the best of him upon coming over from Baltimore last summer (-6 OAA). Cronin induces a high volume of grounders to the left side of the infield, so their execution (or lack thereof) will largely influence his results.

What can Cronin do individually to potentially change his fortunes? Alteration of his pitch mix and usage is something he’s already noted to be working on.

“I haven’t really thrown a true, true sweeper in games since 2023, and even then it was somewhat limited usage,” said Cronin. Throwing the pitch just 5.1 percent of the time in his 11-inning cup of coffee debut season with the White Sox, Cronin featured the sweeper in less than one percent of total pitches thrown in 2024.

“It was something (the Marlins) identified, and not just the pitch itself, but also to allow the rest of the arsenal play up.”

Speaking of that arsenal, further implementation of his four-seam fastball, a pitch he threw just 7.2 percent of the time last year, could contribute to positive regression as well. Cronin throws his four-seamer a half-tick harder than his sinker and misses far more bats with it. The trade-off would be allowing a higher flyball rate, which, in turn, could see him give up a few more home runs than he did the prior year. That's a reasonable gamble when you consider how the pitch induced an average exit velocity of 88.4 mph compared to the 91.6 off his sinker.

A more unpredictable pitch selection would benefit Cronin. A good example I found was this plate appearance against Atlanta’s Eddie Rosario on August 3 last season.

Here’s the sequence: 

• Pitch 1: Sinker outside, ball (1-0). Establishing his fastball to begin the PA.
• Pitch 2: Sinker middle-low, called strike (1-1). Needed to throw a strike with his heater before moving to offspeed.
• Pitch 3: Slider outside, ball (2-1). Finally flashes the breaking ball after two fastballs.
• Pitch 4: Sinker low and inside, fouled off (2-2). Threw a strike with the previous sinker, so went back to it in hopes of evening the count.
• Pitch 5: Slider up and outside, ball (3-2). He’s now attacked Rosario away on four of the five pitches he’s seen. There’s a fifty-percent chance Rosario correctly guesses what Cronin does next.
• Pitch 6: Sinker middle-low, fouled off (3-2). Similar location as Pitch 2, but Rosario stays alive on an early swing.
• Pitch 7: Sinker middle away, single to CF. A good fastball up is the best pitch in baseball. A good fastball that you’ve thrown too many times in the same spot is just muscle memory for a hitter’s eyes.

Expectations for Cronin should be considerably higher in 2025 than they were a year ago when he was an anonymous waiver claim. Even with opponents now being armed with more information about him, the 27-year-old won't be as easy to score upon if his luck starts to even out.