Cardinals recall Cooper Hjerpe from Triple-A Memphis for MLB debut Sunday vs. Rockies

What happened

The St. Louis Cardinals recalled left-handed pitching prospect Cooper Hjerpe from Triple-A Memphis and optioned right-hander Hancel Rincón back to Memphis in a corresponding move, the club announced. Per Derrick Goold of the St. Louis Post-Dispatch, Hjerpe is expected to make his major league debut on Sunday against the Colorado Rockies, following right-handed starter Kyle Leahy.

Hjerpe, 25, was selected 22nd overall by St. Louis in the 2022 draft out of Oregon State. The move brings one of the organization's more closely watched pitching prospects to the big-league level for the first time — though the road here has been anything but a straight line.

Why it matters

The path to Sunday's debut is worth understanding in full, because it runs through two surgeries, a Rule 5 draft scare, and a year in which Hjerpe did not throw a single professional inning.

After posting a 3.37 ERA with a 32.8% strikeout percentage across 93 1/3 innings between High-A and Double-A through 2024, Hjerpe's development stalled. Per MLB Trade Rumors, he walked approximately 14% of hitters from 2023 through 2024, underwent a procedure to remove loose bodies from his elbow during the first of those seasons, and then missed all of last year following a Tommy John procedure. That's the same surgery that, per the newsroom, Cardinals pitcher Hunter Dobbins underwent earlier this week — a reminder of how frequently that particular detour appears on a young pitcher's map.

Facing the possibility of losing Hjerpe in last winter's Rule 5 draft, the Cardinals added him to their 40-man roster. Under general league rules, a player must be on the 40-man roster to be called up to the major leagues, and the Rule 5 draft exposes players not protected on that list — so the club's decision to add him last winter was, in effect, a statement of intent. Sunday is the payoff on that bet.

The Rincón side of this transaction carries its own recent texture. Just days ago, Rincón made his own MLB debut — a moment notable enough that Cardinals manager Oliver Marmol was ejected defending him during the game, and notable enough that an umpire subsequently apologized to Rincón over a cap controversy during that same appearance. That debut, and the circumstances around it, were among the more eventful first impressions a Cardinals reliever has made in recent memory. Now, with Hjerpe needing a roster spot, Rincón heads back to Memphis.

The numbers

Hjerpe's minor-league track record offers a genuinely interesting split between what he can do and what has complicated his development. The 3.37 ERA and 32.8% strikeout percentage across 93 1/3 innings at High-A and Double-A represent the upside case — a left-hander who can miss bats at a meaningful rate. The approximately 14% walk rate from 2023 through 2024 represents the complication. Missing bats and missing the zone at the same time is a combination that tends to keep a pitcher in the minors longer than the strikeout numbers alone would suggest.

The Cardinals enter Sunday at 71-72 (.497), sitting third in the NL Central, 16.5 games back of the division lead. In the Wild Card picture, they rank sixth, 4.0 games relative to the cut line, and are riding a one-game losing streak. The standings context matters here: this is a club that is not in a position to be precious about its September roster construction, which makes a debut for a high-upside arm both lower-stakes and, in some ways, exactly the right moment to find out what Hjerpe is at this level.

Where the club stands

At 71-72, the Cardinals are not a team that can afford to treat the final weeks of the regular season as an extended audition reel — and yet, mathematically, that is increasingly what September looks like. Third in the NL Central and 4.0 games outside the Wild Card cut line, the path to October is narrow.

Sunday's game at Coors Field, where Leahy is listed as the probable starter against Tanner Gordon, is the immediate backdrop for Hjerpe's debut. The Cardinals then travel to Oracle Park to face the San Francisco Giants on Monday and Tuesday, with Logan Webb and Landen Roupp listed as San Francisco's probable starters for those games. The Cardinals' probable starters for those two dates are listed as TBD.

It is worth noting that this series against Colorado is already familiar territory for St. Louis this week. A few days ago, Ivan Herrera's late three-run homer rescued the Cardinals in what was described as an ugly win over the Rockies — so the club arrives at Coors Field having already navigated one uncomfortable afternoon there recently.

What we don't know yet

### Is Hjerpe stretched out enough to handle a multi-inning role?

The club has not specified how many innings Hjerpe is expected to cover in his debut, only that he will follow Leahy. Whether that means a single inning, a multi-inning bridge, or something else entirely is not yet clear from the reporting. Given that he is coming off a Tommy John procedure and has been working his way back through Triple-A, the shape of his workload on Sunday is a genuine open question.

It is also worth noting that his Triple-A numbers from this season have not been detailed in the reporting — the figures available cover his 2023 and 2024 work at High-A and Double-A. How he has performed at Memphis in 2026, as he returned from surgery, is not part of the current record.

The broader question of what role Hjerpe might occupy on this roster beyond Sunday — starter, reliever, multi-inning arm — is similarly unaddressed. The club announced the recall; the job description, for now, is Sunday against the Rockies.

What to watch

The strikeout-to-walk dynamic is the central thing to track in Hjerpe's debut. A 32.8% strikeout percentage is a legitimate weapon; a 14% walk rate is a legitimate liability. At Coors Field, where the margin for error on ball-in-play outcomes is famously thin, the walk rate will matter more than it might in a neutral environment. If Hjerpe can demonstrate that the command issues from 2023 and 2024 have been addressed during his recovery and return, that changes the conversation about what he can be for this club down the stretch. If the walks reappear, the debut becomes a data point rather than a turning point.

Also worth watching: how the Cardinals manage the back end of their rotation over the coming week, with two TBD starters listed for the San Francisco series. September rosters allow for expanded flexibility under general league rules, and the club has shown a willingness to move pieces in and out of Memphis quickly — as this week's Rincón-Hjerpe swap illustrates. Whether Hjerpe stays up beyond Sunday, or whether this is a one-start look before another shuffle, is a question the schedule will answer soon enough.