Cardinals' sidearming southpaw prospect will be shelved for the season

The St. Louis Cardinals received a blow to their pitching depth when it was revealed on April 15 that left-handed pitcher Cooper Hjerpe, their 2022 first-round pick, who was pitching in Triple-A Memphis, will be sidelined until at least mid-2026 after undergoing Tommy John surgery.

Hjerpe had previously been on the 7-day injured list before the move, and he has had issues remaining healthy throughout his brief professional career. He had elbow surgery two months after signing with the Cardinals in 2022, and he injured his elbow again in 2024 shortly after a promotion to Double-A Springfield. The sidewinding lefty has pitched well when healthy, holding a 3.27 ERA across High-A and Double-A in 2025 and striking out an impressive 76 batters in 52.1 innings. But with this latest setback, Hjerpe will have pitched just 93.1 innings since he was drafted.

This isn't the first injury to befall the Memphis rotation. Tink Hence and Quinn Mathews, two of the Cardinals' top-rated pitching prospects, have also been sidelined, with Hence landing on the 60-day injured list and Mathews on the 7-day IL. Neither player has received a definite time table for his return to action.

The last thing the Cardinals want is for Hjerpe to fail to live up to his potential because of meddlesome injuries. Many fans remember Alex Reyes, a high-profile pitching prospect whose career was derailed by a litany of injuries. Hjerpe doesn't hold Reyes' upside, but his run of injuries doesn't bode well for his future. Even with Tommy John surgery's high success rate in the modern day, many pitchers never fully regain their arsenal after it.

The Cardinals received plenty of criticism for keeping Miles Mikolas on the roster, particularly after a terrible start on April 6 that saw him surrender 11 hits and eight earned runs in 2.2 innings, but it may turn out to be a necessary evil as the pitching depth in Memphis continues to drop like flies. Michael McGreevy is one of the few arms whom the Cardinals can call upon with any degree of confidence if an injury were to strike the major league rotation.

The Cardinals' pitching has improved after a rocky start to 2025, and their newly instituted six-man rotation could preserve the health of some of the starters. But with three highly touted young pitchers hitting the injured list for a seemingly extended period of time, their depth is being massively tested.