We Finally Found a Version of Carmen Mlodzinski That Works

I’m not going to pretend that you should care about, or even have heard of, Carmen Mlodzinski before now. He’s a spot starter and medium-leverage reliever on a bad team that gets 90% of its national attention when a specific other pitcher is on the mound. And if you’re not watching the Pirates for Paul Skenes, you’re probably watching them for Bubba Chandler or Mitch Keller or (before he got hurt) Jared Jones, and changing the channel when the bullpen comes in.

It’s fine. Life, unlike Skenes, is short. There are many more important players out there than Mlodzinski.

Nevertheless, he’s doing some fun stuff and I’d like to tell you about it.

On the surface, Mlodzinski had a good 2025: 12 starts plus 22 relief appearances, totaling 99 innings pitched, with an ERA of 3.55 and a FIP of 3.33. He didn’t post gaudy strikeout numbers — his K% was just 21.2%, which isn’t exactly elite closer or no. 1 starter territory — but he posted a career-low 6.4% walk rate and allowed only eight home runs all season.

That looks like a pretty good high-volume swingman season, the likes of which make me get giddy about Ben Casparius every six months. But wait, there’s more.

The Pirates opened 2025 with Mlodzinski in the rotation, and it didn’t go great. Mlodzinski had two or three good outings, but he only made it through five innings twice in his first nine starts, and never made it through six. That led to a demotion in mid-May, and after a month in Triple-A, Mlodzinski returned as a multi-inning reliever.

After Mlodzinski came back from the minors, he made 25 appearances — mostly out of the bullpen, with a couple spot starts in there — and recorded at least five outs on 24 of those occasions. In his second appearance after his furlough to Indianapolis, Mlodzinski had a brutal evening. He entered a tie game in the bottom of the fifth inning and allowed two home runs in two innings against the Tigers, which brought his ERA to 5.98.

In 23 appearances after that bumpy outing, however, Mlodzinski was truly exceptional: 55 1/3 innings, 58 strikeouts, 14 walks, and just one home run in three and half months. His ERA and FIP in that stretch were 1.63 and 2.14, respectively. Just in terms of results, his output down the stretch compares favorably to what much-lauded rookies like Nolan McLean and Trey Yesavage accomplished.

You might say Mlodzinski looked like a different pitcher out there.

The Pirates selected him in the competitive balance round of the 2020 draft, 31st overall, out of South Carolina. In the year leading up to the draft, he’d carved up high-level competition both in the SEC and on the Cape, which, you’d think, would have made him a known commodity at the time.

Mlodzinski was named the Gamecocks’ Friday night starter before his sophomore year. From that point until the moment he got drafted, though, he made only 13 starts between college and the Cape Cod League, totaling only 65 1/3 innings. Not for scary, Tommy John-y or thoracic outlet-y reasons or anything. He took an awkward step while delivering a pitch against Clemson in 2019 and broke a bone in his foot, and then most of the 2020 season got wiped out due to COVID.

What the Pirates had in their hands, then, was a nondescript mass of pitcher-like substance. Mlodzinski is your prototypical right-handed pitcher: 6-foot-2, 220 pounds with a thick lower half. Not a capital-H Hoss, but physical enough to generate above-average fastball velocity from a low three-quarters arm slot, with decent enough command.

Mlodzinski and the Pirates have tinkered here and there, but the basic shape of his delivery hasn’t changed much. What’s come out of that delivery, however, is new every season.

As a rookie, Mlodzinski was a one-inning reliever with one-inning-reliever stuff: a hard four-seamer with more arm-side run than rise — as you’d expect from that arm slot — plus a hard changeup and a cutter for lefties, and a sweeper for righties. That worked well; Mlodzinski had a 2.25 ERA in 35 appearances that year.

Nevertheless, he arrived in 2024 with some new tricks up his sleeve: The changeup was gone, replaced with a slider that sat between the cutter and sweeper. His whiff rates stayed about average, but that gradation of pitches gave him some terrific quality-of-contact numbers. He posted HardHit% and groundball rates in the 75th percentile range, with a Barrel% in the 99th percentile.

But Mlodzinski came into 2025 as a starter, and a starter needs an offspeed pitch. So he got rid of the cutter and added a sinker and a splitter. The sinker has decent separation from the four-seamer, while the splitter comes in a couple miles an hour softer than his old changeup. And while the changeup would veer off arm side, his splitter has similar horizontal action to his four-seamer.

This went quite badly, as you remember. Mlodzinski’s two fastballs were basically fine, though I’m not really convinced the sinker is adding much to the equation. However, opponents slugged .516 against Mlodzinski’s slider and .444 against his sweeper over the course of the season. Early on it was even worse: Through the end of June, his two breaking balls had resulted in 33 whiffs but nine extra-base hits.

Mlodzinski’s sweeper and slider weren’t that great to begin with, and he was not throwing them in a place where hitters would be punished for chasing them. He threw 52.8% of his sweepers and sliders in the zone, which was the 34th-highest percentage out of 241 pitchers who threw 250 or more slider-type pitches in 2025. The guys ahead of him on this list included a few dudes with unhittable breakers — nobody threw more of their sliders in the zone than Tarik Skubal in 2025, and I think you’ll find he did just fine — but also quite a few pitchers like Jordan Romano, who almost got pounded out of the league. Something had to be done.

And look, I understand that pitching is a complicated art, and that a successful arsenal of pitches is like an ecosystem: Take one seemingly unimportant component out and the whole thing might go to pieces.

But sometimes, I dunno, maybe you should try not throwing your worst pitch.

In July, Mlodzinski debuted a curveball for the first time in his major league career. He also shifted his position on the rubber, going from the middle of the pitcher’s plate to the first-base side.

The curveball is nothing revolutionary; it’s got average velocity and movement in all axes. But for the first time in his entire major league career, Mlodzinski was throwing a pitch with appreciable downward induced vertical break. Everything else — fastballs, sliders, offspeed pitches — either rose or ran. Now, he had something he could bury, with relatively little risk of leaving a cement mixer in the center of the zone.

The curveball quickly became Mlodzinski’s best pitch; opponents wOBA’d just .165 off the hook. Both the splitter and curveball started as a new look for use against lefties, but by the end of the season, he was throwing both pitches right-on-right as well. As the season progressed, the other two breaking balls disappeared altogether. In August, Mlodzinski threw 43 curveballs, 12 sweepers, and eight sliders. In September, he threw 73 curveballs, only six sliders, and no sweepers at all.

The results speak for themselves: Opponents went 5-for-26 off Mlodzinski’s curveball, all singles. They only got three extra-base hits — all doubles — off the splitter in 68 at-bats.

Knowing how his career has unfolded thus far, I know better than to predict that Mlodzinski will show up in Bradenton in a couple weeks throwing the same four pitches he was using at the end of the 2025 season. He might have been working on a knuckleball this winter, for all I know.

But the pitcher we saw in the second half of last season was legit. He could be a leverage reliever with that stuff, or continue in his multi-inning bridge role; Mlodzinski had 19 relief appearances of two innings or more last year, tied for second most in the majors. Or the Pirates, having cleared a couple rotation spots in offseason trades, could see how he takes to starting with a better breaking ball.

The options are endless.