Steven Matz’s Forgotten Breakout

He closed out his 2023 as the best Cardinals pitcher.

Throughout the Cardinals’ worst season since 1990, their starting pitching was the easiest flaw to identify. For a “contending team,” having a team-wide starting pitcher ERA of 5.08, which ranked 26th in baseball, is quite a disappointment.

Everyone expected the Cardinals to go out and acquire a handful of arms with the departures of Adam Wainwright, Jordan Montgomery, and Jack Flaherty, which they did. The team inked Sonny Gray to a 3-year, $75M deal, Kyle Gibson to a 1-year, $12M deal, and Lance Lynn to a 1-year, $10M deal, adding three veteran starters to the mix for 2024 and also gave options to Gibson and Lynn for 2025.

Add Miles Mikolas back to the mix and there are your first four starting pitchers, at least according to RosterResource. That leaves us with the last spot, which brings us to Steven Matz.

Matz, who signed a 4-year, $44M contract in 2022, has pitched just 153 innings in his two years in St. Louis. Despite the tumultuous health record with the Cardinals, he was quietly the Cardinals’ second-best starter last year. With Jordan Montgomery getting shipped off to Texas at the trade deadline, Matz’s 3.86 ERA is the best of any returning Cardinal who started a game.

Although he’s getting ramped up slowly after a season-ending lat strain last year, his changes after taking back a rotation spot in late 2023 identify his path to success this year.


The Timeline


Matz had three different stints throughout 2023 across his 25 appearances: he began as a starter, pivoted to a swingman role, and flourished as a starter.

He started 10 games at the beginning of the year with an abysmal 5.72 ERA, 1.75 WHIP, 19.4% K%, and 8.6% BB%. Matz didn’t get through 6 innings in any of these games and the dagger was a 4 IP, 11 hit, 6 earned run outing against the Reds on May 24th, resulting in his first role change.

Matz then moved to the bullpen for a month, where he finally started to get a glimpse at success. In 16 innings over 8 appearances, Matz had a much improved 2.81 ERA, a 1.13 WHIP, 22.7% K%, and 7.6% BB%. Regaining momentum was huge for Matz, who earned an opportunity to start again in July.

Finally, Matz made 7 starts before going down with injury but was lights out beforehand. In 38.2 innings, Matz had a phenomenal 1.86 ERA and 0.88 WHIP over 7 starts. He also posted a strong 25.2% K% and 4.6% BB%. Matz was a different pitcher in this stint, and that improvement started with his sinker.


The High Sinker


You can’t talk about Steven Matz without mentioning how quirky the sinker is. He primarily throws his sinker up in the zone, which generally seems counterintuitive. But it’s always been a successful pitch for him despite its outlier location. Fangraphs’ Ben Clemens recently wrote an article about the high sinker, highlighting Matz as one of the main high-sinker pitchers. My main takeaway from the article is that a high sinker is so counterintuitive that anyone throwing it must be able to do so successfully.

Matz throws the sinker up-and-in to righties and away to lefties, which allows him to put a unique movement & zone combination in front of hitters. This sinker to Elias Diaz shows the fits it can cause for opposing hitters.

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Against righties, Matz has an elite 26.1% whiff rate and a strong .221 xAVG. By locating it up in the zone 61.7% of the time  (98th percentile), Matz can steal called strikes at the top of the zone occasionally too. He doesn’t excel at getting called strikes, but the consistent command around the top of the zone allows him to make competitive pitches to compel swings.

Matz attacks lefties differently, and he does not elevate as frequently. A 40.2% hiLoc% is still well above average, but he throws more pitches in the zone. Matz has an 11% higher zone rate against lefties over righties. The pitch has small reverse splits, with only a 19.8% whiff rate and .263 xAVG against lefties. By not elevating the sinker more, he throws it in locations for hitters to go the other way.

Overall, his sinker locations are extremely outlier compared to others.

Part of Matz’s revival in his second starting stint was the sinker’s velocity. After sitting around 93.5 mph in his first time starting, he was at 94.7 mph at the end of the season. This aligned with his heightened velocity in the bullpen, which he carried through the rest of the season. In addition to velocity, the sinker has good ride, which helps garner whiffs. It gets 10.5 inches of induced vertical break, which is almost three inches more than the 7.8 inches of iVB for the average sinker.

By using the sinker up, Matz has created an opportunity to tunnel the sinker with a low changeup. Usually, the sinker/changeup combination is used for low in the zone and low out of the zone (e.g. Logan Webb), but Matz creates strong north/south separation.


Tunneling with the Changeup


Matz has similar fade on his changeup compared to his sinker, 13.7 inches vs. 14.6 inches, which results in a strong tunnel between the two pitches. As the year went on, these pitches got closer in fade, making the tunnel stronger. With similar horizontal movement, Matz could then target high with the sinker and low with the changeup as it was hard to differentiate between the two. These two pitches against Lourdes Gurriel Jr. achieve just that.

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Although hard to see in the overlay, Gurriel Jr.’s swing on the changeup is a flailing early swing, suggesting he initially saw a high sinker out of the hand.

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Matz relied on the changeup more as a reliever but translated that to increased usage as a starter.

Steven Matz’s 2-Strike Usage

His 2-strike changeup usage as a starter in July and August was also higher than at any point in 2022. According to Alex Chamberlain’s pFIP, the changeup had a 2.04 pFIP in July and 1.93 in August after posting a 4.40 and 5.95 in April and May, a massive step forward.

Matz ended the year with a 28.8% CSW% on the changeup, which ranked in the 80th percentile. The changeup earned called strikes (69.3% strike rate) while getting an average amount of whiffs but was a good enough compliment for the whiff-inducing high sinker. The only issue with the changeup was that it tended to sneak toward the middle of the zone, which led to hard contact.


A Curveball With Potential


Finally, Matz has a big curveball in his arsenal, which took a backseat in his breakout at the end of 2023. The pitch has a large movement profile and is used for called strikes. It’s also the only pitch Matz has that breaks gloveside, so it serves as a change of pace.

It has 80th+ percentile horizontal and vertical movement for a curveball, but it gets thrown high in the strike zone very frequently. Despite underwhelming discipline metrics, it achieves its goal, as it gets called strikes 33% of the time in early counts, 8% more than the league average.

Matz could improve the curveball by getting it down, which could maintain the strong called strike rate but prevent hard contact. I do think Matz is a prime candidate to add a cutter. It would be a second pitch breaking gloveside, but with velocity. This could give Matz a chance to work off the curveball in addition to the sinker. This seems unlikely, but I believe it would take Matz’s arsenal from good to great.


Looking Forward


Matz effectively used a sinker/changeup combo to find success late in 2023. He also had the curveball for strikes, but he showed how he can primarily rely on two pitches to control games.

The Cardinals are being careful with him early on, which hopefully means they are aiming to see his increased velocity at the start of the season. The team already needs as many quality innings from its veterans as it can get, and Matz has the opportunity to be a sleeper in the Cardinals’ rotation.



Nate Schwartz

Nate is currently writing for the Going Deep team at Pitcher List. He is a lifelong St. Louis Cardinals, devil magic, and Matt Carpenter salsa supporter. You can follow him on Twitter/X/whatever @_nateschwartz. Left-handed pitchers make him happy.

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