Cardinals Set Expectations For Cooper Hjerpe After Impressive Debut

The St. Louis Cardinals rookie made history in his debut on Sunday, going four innings without allowing a single base runner.

Sep 6, 2026; Denver, Colorado, USA; St. Louis Cardinals relief pitcher Cooper Hjerpe (56) delivers a pitch in the fourth inning against the Colorado Rockies at Coors Field. Mandatory Credit: Ron Chenoy-Imagn Images | IMAGN IMAGES via Reuters Connect

With injuries piling up down the stretch, the St. Louis Cardinals turned to 25-year-old Cooper Hjerpe in the bullpen, and his debut on Sunday couldn't have gone better.

The Cardinals drafted Hjerpe in the first round of the 2022 MLB Draft, and though he's dealt with a slew of injuries early in his career, he worked his way up to the big leagues. Hjerpe was perfect in his debut against the Colorado Rockies, literally.

The 25-year-old tossed four innings, striking out six batters, but even more impressively, he didn't allow a single baserunner in the 12 batters he faced. Hjerpe joined future Hall of Famer Max Scherzer as only the second pitcher to throw four or more hitless innings with six-plus strikeouts in his MLB debut.

Hjerpe's debut could not have gone better

Feb 26, 2021; Jupiter, Florida, USA; A general view of the St. Louis Cardinals logo on the stadium at Roger Dean Stadium during spring training workouts. Mandatory Credit: Jasen Vinlove-USA TODAY Sports | USA TODAY Sports

Hjerpe made his debut in a long-relief role out of the bullpen, but the left-handed hurler has typically operated as a starter throughout his career. Cardinals manager Oliver Marmol revealed that the 25-year-old won't start for the rest of the season. St. Louis also won't use him as a typical reliever, but will have Hjerpe stay on a starter's schedule and piggyback.

“We will not use him as a reliever,” Marmol said, per MLB.com's Owen Perkins. “He will piggyback, but he will stay on a starter's schedule. That was gross. Everything coming out of the hand was really good. Pounded the zone, over 75% strikes. Fastball was good. Landed the sweeper and the changeup at a super-high rate. Righties, lefties did not look comfortable. That was a lot of fun to watch. He went right after everybody, and good presence, kept his composure all the way through. That was impressive.”

Hjerpe took the spot of Hancel Rincon on the Cardinals' roster after Rincon, who made his debut on Friday, struggled in his first two appearances and was optioned. Through three Minor League seasons, the 25-year-old has posted a 3.26 ERA in 135 1/3 innings with 85 walks and 188 strikeouts.

St. Louis has a bright future with talented young players developing in its farm system. Hjerpe, the Cardinals' No. 18 prospect, is one of the many players who will play a big role in the team's future, and giving him the chance to get more experience is a smart decision.

The Cardinals are still in the mix to earn the final wild-card playoff spot, sitting four games back, but with less than 20 games remaining, it seems unlikely they'll reach the postseason. Despite that, this season has been a complete success, with players like Hjerpe getting a shot in the big leagues.