It Doesn't Seem That Way At First Glance, But Steven Matz Makes A Lot Of Sense For The 2025 Red Sox

Late on Wednesday, July 30, the Red Sox traded prospect Blaze Jordan for LHP Steven Matz from the St. Louis Cardinals. Talk Sox’s Nick John was quick to get an overview of the deal. I’ve highlighted Matz a couple of times over recent weeks, but admittedly, it's hard to see the fit because he’s another left-handed reliever. After diving into some deeper numbers and splits, I’ve come around, and the deal for Matz helps to solidify the bullpen in a solid way. He follows what the Red Sox like for their pitchers to do; he induces groundballs and has nasty secondary offerings. 

A Look Under the Hood
Matz currently has a 3.44 ERA with 47 strikeouts in 55 innings pitched. He’s worked as an opener twice this season and has notched a single save. His strikeout percentage is sitting at a solid 20.7% while his walk rate is an impressive flat 4%. That walk rate puts him in the top 2% of pitchers in baseball. His home runs per nine is the lowest it has been in his career at 0.65, and he has a career low in FIP at 2.87.

To go along with his 44.3% ground ball rate, he’s getting hitters to make contact over the top of the ball at a 37.6% clip, which makes sense when you look at his pitch mix. He relies heavily on a sinker that averages 94.3 MPH. He then features a curve and changeup that average 79.4 MPH and 83.8 MPH, respectively. He has a slider that he keeps in his pocket, but rarely uses it, with just two percent on the season so far. That being said, Andrew Bailey loves a good slider, so if he believes that Matz can tap into something with it, then it may become more than just a fourth option pitch for him. 

A Converted Starter
It’s no secret that Matz began his career as a starter with the Mets. He found success early in his career in this role, but floundered over the last couple of seasons after landing in St. Louis. To combat that, the Cardinals moved him to the bullpen in May of this year, and it seemed to unlock a new level for him. He’s already topped his strikeout numbers from last season, although that was an injury-shortened season for him.

Looking at his last full season as a starter in 2023, we see that the numbers that matter are all down across the board for Matz. His average against is down a hair from .263 to .260, his slug against is down from .405 to .377, and his wOBA is down from .316 to .292. He’s found a role that serves his pitching style well in the bullpen and looks to continue that dominance in Boston. The Red Sox are expected to keep him in his bullpen role, but his starting history could have him begin some games as an opener to help keep the starting rotation fresh as we navigate the dog days of summer. 

LOOGY Potential
Although Matz is a left-handed reliever, the Cardinals didn’t use him in a way that showcased his strengths. He’s thrown 24 innings against left-handed hitters and 30 2/3 innings against righties. He has faced more righties than lefties, 138 to 89, and has performed much better against lefties on the season. His slash line against hitters of different handedness shows that in Boston, he’s likely going to be seeing far more left-handed hitters than right-handed hitters. Lefties are slashing .179/.216/.226 with a .199 wOBA while righties are faring far better by slashing .313/.341/.473 with a .351 wOBA against him

Against left-handed hitters, he uses his sinker 25.5% of the time and his curveball 10.7% of the time. He all but abandons his changeup and slider, using them 1.1% and 0.8% of the time, respectively. Against right-handed hitters, he uses his sinker 33.8% of the time, and his change-up becomes his secondary pitch at 16.9% of the time, while his curveball and slider see a 9.8% and 1.2% use rate.  It seems logical, but making Matz a left-handed specialist is the path Boston is looking to take here. They already have left-handed help in the bullpen with Aroldis Chapman, Justin Wilson, Brennan Bernardino, and Chris Murphy already on the roster. Still, Matz should slot in before all of them except Chapman.

I don’t expect the Red Sox to be done as the trade deadline is mere hours away, but adding Steven Matz is a great step in the right direction for the club. Only giving up Blaze Jordan, a prospect who was blocked at both positions and would surely be taken in the Rule 5 draft next year, is a steal for Craig Breslow. Matz adds a left-handed specialty that the bullpen needs, even if that means other relievers have to be moved to accommodate him.