Why this Pirates reliever could be in for a huge breakout in 2025

Pittsburgh Pirates reliever Carmen Mlodzinski is coming off a quality 2024 season. He pitched to the tune of a 3.38 ERA, 3.36 FIP, and 1.18 WHIP across 50.2 innings. The former first-round competitive balance pick had a roughly league-average 22% strikeout rate and a 9.1% walk rate, but he was excellent at limiting home runs. Mlodzinski’s HR/9 rate was just 0.53, and he ranked in the 99th percentile of barrel rate at 2.3%.

Mlodzinski has now proven himself to be a quality relief option for the Pirates, as this was his second season in a row where he gave the Pirates reliable innings out of the bullpen. Still, there are a few noteworthy reasons why Mlodzinski's forward steps might only be a preview of things to come. If everything continues progressing, 2025 could be a huge breakout year for the right-hander.

One of the main reasons why Mlodzinski could have a big 2025 breakout is because of his huge uptick in pitch quality between 2023 and 2024. Stuff+ is a measurement of how good a pitcher’s offerings are, based on characteristics such as velocity, spin, movement, and release point. Like other statistics that end with a plus sign, 100 is typically average.

Pirates reliever Carmen Mlodzinski's stuff improvement should portend breakout 2025

In 2023, Stuff+ put Mlodzinski’s pitch mix at just 87, but this past season, he saw that jump to 104. His four-seamer saw a significant increase from 85 to 95 because he took off over an inch of vertical drop from 17.5 inches to 16.1 inches while maintaining similar velocity (95.7 MPH to 96.2 MPH) and horizontal movement (10 inches to 9.7 inches). This helped give his fastball a better riding effect through the zone. This change may have helped him induce more swings and misses, as his whiff rate on his four-seamer went from 20.4% in 2023 to 25.5% this past year.

Mlodzinski also started to throw a slider. He threw this pitch in the upper 80s with about 40 inches of drop and 3.4 inches of break. This slider is another reason why Mlodzinski could be in store for a 2025 breakout campaign. This was one of his most effective offerings, as it held opponents to a .248 wOBA, the lowest of his four pitches. Opponents also swung and missed at his slider 32.1% of the time. Only his sweeper induced a higher whiff rate of 33.9%.

Also, keep in mind that Mlodzinski has yet to pitch a full season in the Major Leagues. The Pirates didn’t call him up until mid-June during his rookie year in 2023. Then, in 2024, Mlodzinski missed part of April recovering from an injury suffered during spring training. He didn't make his season debut until mid-May, taking extra time to warm up for the year. 

A fully healthy Mlodzinski who pitches the entire year could be a force to be reckoned with out of the Pirates’ bullpen in 2025. He could easily be the Pirates’ go-to eighth-inning set-up man, and you can’t rule out Mlodzinski even seeing a handful of save opportunities. The improvements he made in 2024 were very promising, and it should be entertaining to see how he can continue to trend upward next year.