If Cooper Hjerpe was feeling the nerves during his MLB debut on Sunday, he didn’t show it.
The left-handed pitcher was on the mound for the St. Louis Cardinals against the Colorado Rockies, and it would’ve been tough for him to be any sharper than he was.
He came on in relief and then put together an exceptional statline.
Hjerpe went 4.0 innings. He faced 12 batters. None of them reached base.
In the process, Hjerpe struck out six hitters.
He threw 54 pitches, 41 of them for strikes.
And he did it all in Coors Field, which should be just about the toughest ballpark for a pitcher to make his MLB debut and maintain optimal effectiveness.
Hjerpe earned the pitching win, too, because the Cardinals took the lead with him on the mound by putting up six runs in the top of the fifth inning in an eventual 10-8 victory.
Cooper Hjerpe MLB History
Hjerpe was just the third pitcher with a line like his in the history of the sport.
According to MLB stats guru Sarah Langs, he had the third-longest outing with no baserunners allowed in an MLB pitching debut since at least 1900.
Max Kranick had the longest such outing when he went 5.0 innings and didn’t allow a baserunner in 2021.
Future Hall of Famer Max Scherzer had one longer than Hjerpe as well, going 4.1 innings without allowing a baserunner in his MLB debut in 2008.
Turns out your name doesn’t have to be Max to be on that list, as Cooper Hjerpe now gets himself involved in that history, too.
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
Cooper Hjerpe Fast Facts
Hjerpe does have a strong pedigree that would’ve pointed to the potential for MLB success.
He was a first-round pick, No. 22 overall, by the Cardinals in the 2022 MLB Draft out of Oregon State.
The 6-foot-3, 200-pound lefty is originally from California, where he attended Woodland High School.
He was a strong performer in his first two professional seasons. In 2023, he had a 3.51 ERA at High-A Peoria. Then he split the 2024 season between Peoria and Double-A Springfield, putting up a combined 3.27 ERA.
Hjerpe’s development was stunted by an injury that kept him out of the entire 2025 season.
This year he returned and worked his way back up the ladder to get to Triple-A Memphis, where he had a 0.95 ERA in five appearances before his promotion to St. Louis.
In his minor league career, Hjerpe has struck out 12.5 batters per nine innings, which shows his potential dominance, although he has also walked 5.7 guys per nine innings, a rate which is a bit too high.
Clearly, if he can find his control and use his best stuff, Hjerpe can get major league hitters out. In his debut, he did it in historic fashion, and now it’ll be up to him to make sure he puts together a solid encore.
Cardinals’ Cooper Hjerpe Makes Baseball History in MLB Debut