Asking if a player is on the verge of a breakout is the quintessential question when it comes to analysis. Understanding why someone believes a player is ready for an unexpected performance boost is what elevates a good team to a great team, or even transforms the long-term perspective of a current team’s structure.
Now, debating breakout skills usually comes before we see the on-field improvement, but in Matthew Liberatore’s case, the jury is still out. The 25-year-old has been the seventh most valuable starter by fWAR this season, with most of his early-season peripherals suggesting a significantly better outcome than his 3.19 ERA.
Despite the strong start, Liberatore’s path leading up to this season has been a winding one.
He was drafted 16th overall in the 2018 draft by the Tampa Bay Rays before coming to St. Louis in exchange for Randy Arozarena before the 2020 season. Baseball America ranked Liberatore as high as 42nd on their 2020 Top 100 prospects list, describing him “as safe a bet as a teenage pitching prospect can be.”
Without a minor league season in 2020, the Cardinals aggressively promoted Liberatore to Triple-A in 2021. His 2021 showed progress with a respectable 4.04 ERA in 124 innings, but his development seemingly stalled with a 5.17 ERA in AAA in 2022. Regardless, Liberatore got his shot with the big league club in 2022. He debuted in May, posting a disappointing but not unexpected 5.46 ERA across seven starts. He was optioned a handful of times and came back to make two relief appearances late in the year as well.
2023 was more of the same, as he spent an equal amount of time in Triple-A and MLB with an ERA above 4.00 in the minors and above 5.00 in the majors. However, one development started to emerge: Liberatore held a 2.84 ERA in 12.2 innings as a reliever, striking out 24.5% of the batters he faced. Could he follow the line of failed pitching prospect to dominant reliever pipeline?
The Cardinals seemed to think so, at least last year. Liberatore spent all of 2024 with the big league club, appearing in 60 games with only six being starts.
Naturally, this would lead everyone to believe that Liberatore was on track to become a mainstay in the back of the Cardinals’ depleted bullpen heading into 2025. Instead, in the Cardinals’ “reset” year, they gave him another shot as a starter.
For as much as Cardinals fans like questioning their front office (myself included), this decision has worked out so far. Liberatore hasn’t posted a sub-4.00 ERA season at any level with the Cardinals so far, but 2025 looks different.
Liberatore’s changes can be viewed through the perspectives of two players: Clayton Kershaw and Max Meyer. Two wildly different players with various paths, but each has specific aspects to their development at the big league level that Liberatore is using.
Following the Path of Greatness
Liberatore’s large-scale developments are similar to those of the all-time great left-handed pitcher, Clayton Kershaw.
While extreme, Liberatore shares many similarities with the future Hall of Famer, even if the ceiling isn’t the same. Both are high armslot lefties with an elite slow curveball and non-overpowering velocity.
While Liberatore’s has a bit more velocity and less drop, it features similarly large shapes coming from an over-the-top release. Stuff+ grades both pitches as 120 or greater in recent years.
Early in Kershaw’s career, he struggled to put away hitters, especially right-handed hitters, with the fastball/curveball combo. The changeup never really stuck for him, leaving him desperate for a third pitch. However, once he found his slider, the Hall of Fame case began to build. Kershaw’s slider quickly became his second pitch in his prime and has been his primary pitch since 2021; the curveball has averaged only 16% usage throughout most of his career.
For Liberatore, he had more pitches when he debuted, but also struggled as a primarily fastball/curveball pitcher. He’s tweaked the arsenal across his four MLB seasons so far (which I’ll get to later), but like Kershaw, the introduction of the slider has been critical to his success vs. right-handed hitters. Having the curveball to freeze hitters is still in the back pocket, but it’s not the centerpiece of his arsenal like it was in his days as a top prospect.
The slider has become the core of the arsenal, posting a 36.2% CSW% as his primary pitch. Unlike Kershaw, Liberatore altered the shape of his slider to have more drop movement, creating a pitch that is more platoon-neutral.
While this isn’t going to put Liberatore on a similar Hall of Fame track, it’s essential to recognize that left-handed pitchers require a different set of pitches to deal with right-handed batters than right-handed pitchers. Liberatore has a similar release and has revamped the slider to take over, which is reminiscent of Kershaw. Especially in today’s game, the fastball/curveball as a lefty is not going to work.
So About This Slider…
Liberatore has changed the shape of his slider, adding more drop this season while relatively maintaining velocity.
The increase in 2024 comes from his time relieving, but he was able to take those gains and bring more drop to the slider at a higher velocity. While the Stuff+ of the pitch decreased from last year (111 vs. 120), its effectiveness has increased significantly.
The additional drop has helped Liberatore keep the slider down, preventing significant damage and missing bats. He has also been aggressive about throwing pitches in the zone with higher usage, and it’s paying off.
Even though the slider has a high mistake rate, it’s the low mistakes that hitters aren’t doing anything huge with. The mistakes result in hard contact, primarily in the form of groundballs and low line drives. While the ICR rate is a bit high, there has yet to be an extra-base hit against the slider this year, and hitters have never hit a home run off the pitch in Liberatore’s four years in the big leagues.
Mistakes also indicate that Liberatore’s command has improved significantly. While just seeing the marginal increase in zone rate is nice, it doesn’t tell the whole story. Liberatore is getting around more sliders and confidently burying them in the zone, rather than letting them sail in either direction.
Just 3.9% of Liberatore’s sliders are armside, compared to the 21.2% league average. Meanwhile, the amount of waste pitches to his glove side is now at a league average of 9.8%.
By limiting the pitches that get away, there are inherently going to be more whiffs and more called strikes.
Following the Path of a Fellow Breakout
Equipped with a dominant slider, Liberatore still needed to fill out the rest of the arsenal in order to be a successful starter who could deal with a lineup multiple times. A pitcher who was faced with a similar dilemma heading into this season is Marlins starter Max Meyer.
Meyer was also a highly touted prospect before making his big league debut in 2022, but underwent Tommy John surgery, which required him to miss most of 2022 and all of 2023. Meyer was successful only with the slider in 2024, as he posted an underwhelming 5.68 ERA in 57 innings. The slider had a 31.0% CSW%, but no other pitch was above 24%, making him a one-trick pony.
This season, he’s incorporated a handful of pitches to work around the slider. Meyer revamped his changeup and added two new pitches, a sinker and sweeper. The alterations to his changeup were adding a significant amount of drop (six inches) and a touch of armside run. The sinker works to force weak contact off the fastball, and the sweeper has been a called strike pitch.
All of this doesn’t change the fact that Meyer’s fastball isn’t great and still allows a lot of hard contact without generating many whiffs. Instead, there are enough other pitches near the plate that make a hitter forget about the slider, only to fall victim to it once again.
Meyer also added a tick of velocity everywhere, but his slider now has a 39.0% CSW% fueled by a ridiculous 26.3% SwStr%. At 39.8% usage, it’s okay that the other pitches may not be as effective as they need to be.
Circling back to Liberatore, he also needed to make everything else work around the slider. He was already throwing secondary fastballs with poor results, but needed to refine his changeup, too.
Liberatore added around a tick of velocity, three inches of run, and two inches of drop. Adding velocity and drop simultaneously is an impressive combination, as gravity usually prevents that from happening. The pitch doesn’t necessarily grade out better by Stuff+ (85 vs. 83), but he’s throwing it with more confidence in the zone. The increased zone rate is challenging hitters to make a decision, something they didn’t have to do in years prior.
Whether it’s a new grip or adjustments on the changeup, Liberatore has significantly reduced the high-and-armside mistakes and is fully attacking the zone.
Liberatore doesn’t need these pitches to help put away hitters, but instead works to the two-strike counts when he can then turn to the slider.
Liberatore isn’t as aggressive as Meyer when it comes to the slider usage in two-strike counts (Meyer is above 60%), but it’s still a dominant pitch. With that being said, the slider works because the rest of the arsenal is passable, which needs to be maintained for success to continue.
The Fastball Holds All
Most damage comes early in the count, which is why it’s so important for Liberatore to have enough pitches to make it later in the at-bat. Liberatore’s fastball velocity has increased slightly (akin to Meyer), but there is a reverse result compared to what you’d expect.
Liberatore’s fastball averages 94.3, but when thrown above 94 mph, it performs significantly worse. The whiff rate is slightly higher at higher velocity, but not by much. The harder fastballs are also in the shadow part of the zone more than the slower ones, but are getting hit for almost twice as much damage.
This early in the season, this could still be noise. It wasn’t the case last year, but it is the one thing that leaves the door open for improvement in this performance.
The sinker remains an average pitch that does just enough in the arsenal, while the cutter’s command is flourishing.
When you can count on one hand how many pitches are over the middle of the plate, that’s quite a good sign. It’s earning whiffs off the plate against lefties and weak contact & called strikes against righties, perfectly fulfilling the role of a cutter.
The cutter boasts an exceptional 27.3% ICR, exemplifying the nature of a contact-suppressing pitch that bridges the gap between the slider and fastball.
The Verdict
The 2025 Liberatore has shown significant developments across his stuff and command, resulting in an exciting 3.19 ERA and 0.97 WHIP so far.
By taking steps forward in a previously established way (via that of a Kershaw or Meyer), it’s clear to see how success continues. Multiple fastballs limit overall fastball damage, while the improved changeup is able to steal called strikes, setting up the devastating slider with two strikes. And if you focused too much on the new, he can still freeze you with the old.
Liberatore has the most confidence we’ve seen at the big league level so far, which is part of why he can throw his pitches in the zone more effectively. The execution has resulted in a 104 Pitching+, ranked 34th among qualified starters, which doesn’t come as a fluke. This is the strongest case Liberatore has presented on how he can be an every-fifth-day starter, but there are still some small hesitations.
The 1.7% walk rate will likely come up: I don’t believe the changeup will earn this many called strikes as teams get more looks at Liberatore, forcing him to bury the pitch more. Additionally, the HR/9 is unlikely to remain at 0.29. These stats are both a testament to how well he’s executing, but both would instantly become near the top of the league figures if they hold. Regression will come for both, but not necessarily in a debilitating way.
Finally, the fastball’s confusing performance makes me wonder if there’s a larger batted ball regression coming. If hitters are somehow only damaging the better-executed high-velocity pitches, it may only be a matter of time before the softer fastballs get hit too.
Regardless, I think Liberatore crafted the potential to be a 3.60ish ERA pitcher with a 22% strikeout rate. He’s showing a repeatable path to success and finally carving out a role that Cardinals fans expected from him, giving much-needed life to the team’s future pitching outlook.
Really well done analysis of a young pitcher finding another level. Liberatore is learning how to pitch at the big league level and actually had a few hard luck innings earlier in the year or his ERA would be even lower. Interested to see how this plays out, I think he has the arsenal to continue his progression and possibly continue to breakout in 2025.
Liberatore’s breakout feels real—Cardinals may have found their ace.