Move Over Max Scherzer: Cooper Hjerpe's Perfect Cardinals Debut Makes History

As injuries piled up in the St. Louis Cardinals' starting rotation, a handful of hurlers popped up as potential fits to be promoted to help to minimize the workload.

Andre Pallante is back from the Injured List, but Hunter Dobbins is done for the season and Kyle Leahy has had his innings limited. In response, the Cardinals promoted former first-round pick Cooper Hjerpe to make his big league debut on Sunday and piggyback off Leahy.

Leahy got the start and went 2 2/3 innings while allowing five runs. Cade Winquest entered in relief of Leahy and tossed 1/3 of an inning. Then, the hill was turned over to Hjerpe and he was perfect. No, that's not an exaggeration. He was perfect.

Perfection For Cooper Hjerpe

Feb 17, 2026; Jupiter, FL, USA; St. Louis Cardinals pitcher Cooper Hjerpe (56). Mandatory Credit: Jim Rassol-Imagn Images | IMAGN IMAGES via Reuters Connect

Hjerpe tossed four innings and struck out six batters without allowing a base hit or walking anyone. 12 up, 12 down.

Cooper Hjerpe dominated in his big league debut 😤

4 IP
0 H
0 ER
0 BB
6 K

He ranks No. 30 in the Cardinals’ system.

(🎥@Cardinals) pic.twitter.com/Ms7D6TRCJQ
— Baseball America (@BaseballAmerica) September 6, 2026

Unsurprisingly, when you toss four perfect innings in your MLB debut, that comes with some history. Hjerpe became the second pitcher since 1904 to throw four or more hitless innings with six-plus strikeouts in an MLB debut. Hjerpe joined future Hall of Famer Max Scherzer with that performance, per Just Baseball.

Cooper Hjerpe in his MLB debut today:

4 IP | 0 H | 0 ER | 0 BB | 6 K

He's just the second pitcher since 1904 to throw 4 or more hitless innings with 6+ strikeouts in a MLB debut. The other? Max Scherzer 🤯 pic.twitter.com/HJdNamiLgh
— Just Baseball (@JustBB_Media) September 6, 2026

Hjerpe also just put together the third-longest MLB debut without allowing a baserunner in general, per MLB.com's Sarah Langs.

"Longest outing in MLB debut with no baserunners allowed, since at least 1900: 6/27/21 Max Kranick: 5 IP, 4/29/08 Max Scherzer: 4 1/3 IP, 9/6/26 Cooper Hjerpe: 4 IP," Langs wrote.

Longest outing in MLB debut with no baserunners allowed, since at least 1900:

6/27/21 Max Kranick: 5 IP
4/29/08 Max Scherzer: 4 1/3 IP
9/6/26 Cooper Hjerpe: 4 IP https://t.co/U0F92DWXnL
— Sarah Langs (@SlangsOnSports) September 6, 2026

Plus, he became just the second pitcher in Major League Baseball history to throw four or more perfect innings of relief in an MLB debut.

Couldn't cool off Coop today 🔥

Cooper Hjerpe became just the second pitcher in Major League history to throw 4.0 or more perfect innings of relief in an MLB debut! pic.twitter.com/xZ00dzNy1q
— St. Louis Cardinals (@Cardinals) September 6, 2026

The list goes on and on. Simply put, Hjerpe was incredible and lived up to the hype in his MLB debut.

It's been a big year for the lefty. He missed the 2025 season and returned to the hill this season. He has pitched for the FCL Cardinals, Class-A Palm Beach, Double-A Springfield, Triple-A Memphis and now the Cardinals in the majors. Hjerpe had never pitched above Double-A and now he's tossing perfect innings in the majors a year after missing the entire 2025 season. You couldn't ask for much more out of a young hurler at this point.

These next few weeks will be a test for this young Cardinals roster. The Cardinals are four games out of a playoff spot. Even if they don't close that gap, these next few weeks will play a big role on the 2027 club. For example, there will be a lot of young guys fighting for just a few rotation spots. Hjerpe is one. If he looks as good for the rest of the season as he did on Sunday, he's going to give himself a real shot at landing a significant spot in 2027.

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