Of all the former first-round picks who made their major-league debut with the Pirates this year, the team's 2023 WAR leader among first year players was a bit of a surprise. It wasn't Henry Davis, Quinn Priester, Nick Gonzales or Alika Williams. It was the pitcher who converted to a reliever that year: Carmen Mlodzinski.
The Pirates' bullpen got significantly younger this season, featuring 10 rookies who pitched as a reliever (including bulk guys who followed an opener). Of the 626 1/3 innings the bullpen threw this year, nearly one-third of those innings were from a rookie (196 1/3 innings, the most in the National League). The unit had some mixed results, but for a team that didn't have much of a bridge to David Bednar coming into the year, Colin Holderman and Mlodzinski served well.
Not only did Mlodzinski have the best rookie season for a Pirate reliever since Bednar, he can stake claim to one of the better seasons ever for a Pirate rookie. I put into Stathead which Pirate rookie relievers could match or better his ERA (2.25) while also appearing in at least 30 games (Mlodzinski pitched in 35), and it's a pretty short and impressive list:
What's interesting is Mlodzinski has become one of the Pirates' better bullpen arms with a very different pitch mix compared to when he was drafted.
Back in 2020, Mlodzinski was primarily a sinker-slider guy, with the latter pitch still evolving from a cutter. Since then, he has essentially ditched the sinker and turned that slider back into a cutter, while adding a sweeper to the mix in 2023. You won't find too many relievers who have two different breaking balls at their disposal, but that gives Mlodzinski a unique weapon that he can change based on the batter.
"I think it's important to have two offspeed pitches or two breaking balls, because over the course of the season, guys are going to get a report on you," Mlodzinski told me at the end of the season. "Having two different types of pitches that can break off of your fastballs is extremely important."
While Mlodzinski can throw both breaking balls to righties and lefties, he definitely leaned more with the sweeper against right-handers (77.9% of the time) and cutters for left-handers (76.5%). Those pitches don't always behave quite like how a traditional sweeper and cutter would.
The sweeper, in Mlodzinski's mind, is more of a slurve. It averaged 14.5 inches of horzontal movement, which is 1.4 inches more than average. That's solid, but the eye-opener is that 41.4 inches of vertical movement, which is 4.9 more inches of drop than average. Across the league, this is widely known as a horizontal pitch, one that can run away from same-handed hitters. Mlodzinski can use it for that, but it's also a drop pitch.
To look at it another way, the guy who used to rely on vertical movement with the sinker is finding a new way to get that downward movement.
When it's clicking, look at what his high-spin breaking pitch can do:
There's a ton of horizontal break there, but it only works because of the downward bite. Without it, he is just jamming the batter with a breaking ball inside.
It's tougher to measure the cutter's break because he actually has two different types of cutters based on the batter. As the season progressed, he learned how to kill some vertical movement by making it more of a gyro spin pitch, while he could still bury it down and in to left-handers. If that sounds familiar, it's because he took direct inspiration from Mitch Keller and how he makes an "X" with his cutter and fastball.
"He was kind of the outline, I would say," Mlodzinski said. "It's something I looked into, the way he throws it to right-handed hitters."
That cutter was sitting about 87-90 mph in 2022, but averaged 91.9 mph in 2023. Mix in the different pitch shapes and velocity, and it makes sense why Mlodzinski is able to have two breaking pitches that perform really well despite them landing in very similar parts of the plate:
That leaves just one question: What is the encore going to be like?
The Pirates are going to look at reliever options this winter, but Ben Cherington said in his end-of-season media availabililty that the focus is going to primarily be the rotation and hitters. Something could potentially change if the right opportunity arises, but it seems safe to assume that the team is counting on Mlodzinski to be a leverage reliever again. He had a great rookie season, but relievers tend to be fungible and inconsistent. For every Bednar, there tends to be two or three Kyle Crick's.
Mlodzinski's underlying peripherals were not as impressive as his ERA, though they were far from bad for a rookie (3.96 expected ERA, 4.03 FIP). There was some hard contact mixed in there and a higher walk rate (11.8%), but his whiff percentage was also over 20% for all four of his pitches (including the changeup) and he has ways to up that 22.4% strikeout rate.
Mlodzinski is one of the most fascinating pitchers in the Pirates' bullpen going into next year. He can still get the vertical bite which leads to a lot of ground outs, but embracing more horizontal movement has helped him up his strikeout rate and made him a viable reliever. There's always a risk putting too many eggs in the young reliever basket, but the Pirates have a good collection of young arms in that bullpen. They'll need them if they want to take a step forward next year.
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