Liberatore is Cardinals’ leftybullpen weapon. Does that mean he’s done as a starter?

A major part of the preparation the St. Louis Cardinals underwent last offseason in their quest to shake off an entirely last year was figuring out how to maximize the output they received from closer Ryan Helsley.

To do that – to comfortably slot him in exclusively in closing situations – required a personnel upgrade.

The acquisition of Andrew Kittredge from the Tampa Bay Rays was a major step in that, as was signing Keynan Middleton as a free agent. Middleton has missed the season with an arm injury but has had his slot more than capably filled by Rule 5 selection Ryan Fernandez, keeping all of the relevant pieces in place.

The last piece which clicked in – and which didn’t fully click in until June – was the team’s commitment to Matthew Liberatore as a versatile bullpen lefty, allowing the rest of the puzzle to come together seamlessly.

“For your story, you can basically look back at the day he started being good, and say it was the day before,” manager Oli Marmol joked when asked about any conversation that might have been a turning point in Liberatore’s season.

Kidding aside, Marmol is not far off.

Since his most recent start on July 24, Liberatore has allowed 11 earned runs in 22 ⅔ innings pitched, striking out 24 hitters and walking only six. That’s good for a 4.37 ERA but a Fielding Independent Pitching mark of just 3.13, which is to say he’s pitched into bad luck and less than stellar defense behind him.

Of those 11 earned runs allowed, eight came in just two appearances. One of those was his first appearance after moving permanently back to the bullpen, meaning that he’s turned in a shutout appearance in 14 of his 18 games since the end of July.

This version of Liberatore looks a lot like the pitcher the Cardinals often dreamed could be a standout starter for them, but who is instead blossoming to a dangerous lefty weapon to group with JoJo Romero and John King.

As with any reliever, part of Liberatore’s move to the bullpen has been a simplification of his arsenal. As a starter, he worked largely through a five-pitch mix, but his work from the bullpen has turned him largely into the fastball-slider combination lefty that has had so much success in the modern game.

In utilizing two fastballs, both a four-seamer and a sinker, he has the ability to cut with velocity in opposing directions. His slider usage has jumped from 12.7% to 27.4% year over year, and as a corollary, his frequency of curveball usage has cratered from 22.4% to 6.4%.

So much of modern pitching is figuring out not just how pitches behave, but how they behave in relation to each other. For Liberatore, replacing his curveball almost entirely with a more effective slider has created more deception and pushed up the effectiveness of his fastball. That effect is magnified by his ability to dial up velocity in shorter burst outings rather than having to pitch the intent of getting deeper into games, and the data again demonstrates the effectiveness of that change.

What’s most striking about Liberatore’s pitch data is that the deliveries leaving his hand in 2024 are nearly identical in speed and shape to those he provided in 2023. What’s different is simply their effectiveness; his fastball has gone from a negative to a positive run value, and hard hit percentage against the pitch has dropped from 46.6% to 40.4%.

So much of that comes down to necessary respect for the suddenly prominent slider. In 2023, that pitch was worth negative five runs and carried a 34.8% hard hit percentage. In 2024, it has instead generated a positive run value of four, and is only hit hard 28.1% of the time.

Reshaping an entire arsenal can be necessary for some pitchers, but isn’t always if there have been issues of selection which otherwise poisoned the well. By cratering his curveball usage and working the slider off of his two fastballs, Liberatore has created a far superior tunneling effect that allows him to keep hitters guessing and generate a better swing and miss percentage against pitches that looked pedestrian in another context.

Wednesday’s win over the Reds was a demonstration of that effectiveness. By being able to slot Liberatore into a lane as early as the sixth inning of a tie game, it allowed Marmol to set Kittredge and Romero for their preferred matchups in higher leverage situations later, bridging the game to Helsley in the ninth.

Liberatore’s work in that game didn’t show up among the wins and losses in the box score, but it was a vital component of a victory that, like so many others for the Cardinals this season, came late and narrowly.

The Cardinals aren’t yet prepared to publicly close the door on Liberatore as a starter, with Marmol saying only that he’s pitched well out of the bullpen and he’s happy to see him finish the year there. Whatever happens in the next few months, though, it’s clear that what happened in the last few have ramped up his effectiveness and allowed him to compete at the level long desired.

That success seems to be less the result of any single talk and more the result of figuring out that more, in Liberatore’s case, was generating a whole lot less.