Jacob Misiorowski's major league debut for the Milwaukee Brewers on June 12, 2025, was nothing short of electric as the 23-year-old flamethrower dazzled fans and teammates alike with a masterful performance against the St. Louis Cardinals at American Family Field. The lanky right-hander held the Cardinals hitless for five innings before a freak injury prematurely ended his night, but not before he etched his name into Brewers history with blazing fastballs and a commanding presence on the mound.
From the very first pitch, Misiorowski announced his arrival with authority. His initial offering clocked in at 100.5 mph, the second-fastest pitch by a Brewers starter since pitch tracking began in 2008, just shy of Trevor Megill’s 100.7 mph as an opener in 2023. The velocity only climbed from there, with his second pitch reaching 101.8 mph and his fifth an astounding 102.2 mph — the fastest pitch ever thrown by a Brewers starter in the pitch-tracking era. Over the course of his outing, Misiorowski fired 14 pitches at or above 100 mph, a feat matched by only a handful of pitchers during their MLB debuts.
His electric fastball was complemented by a diverse arsenal, including 24 sliders, 11 curveballs, and two changeups, showcasing not only raw power but also pitchability. He averaged 99.1 mph on 41 four-seam fastballs, consistently challenging the Cardinals’ lineup with both speed and movement. The result was a dominant five innings without allowing a hit or a run, peppered with five strikeouts and four walks over 81 pitches. Misiorowski’s ability to generate 13 swings and misses, including seven on fastballs alone, demonstrated his potential as a future ace.
Despite the nerves that naturally come with a major league debut, Misiorowski handled the moment with poise. “I felt amped up and had to relax myself,” he admitted, recalling the second inning. “That second inning was like, ‘Calm down. You’ve got this. It’ll be fine.’” His confidence was well-founded as he navigated the heart of the Cardinals’ lineup with precision, striking out key hitters like Willson Contreras and Nolan Gorman on pitches exceeding 100 mph.
The Brewers’ offense provided crucial support early on, breaking the deadlock in the second inning with a two-out triple by rookie Isaac Collins followed by an infield single from Brice Turang that scored the game’s first run. Milwaukee then exploded for five more runs in the fifth inning, highlighted by Sal Frelick’s two-run single and Jackson Chourio’s two-run homer, effectively putting the game out of reach and allowing Misiorowski to pitch with a comfortable lead.
However, the night took a tense turn in the sixth inning. After throwing three consecutive balls to Victor Scott II, Misiorowski’s right foot landed awkwardly on the mound, causing him to roll his ankle and cramp in his right calf and quadriceps. The injury forced him to exit the game amid a standing ovation, leaving relief pitcher Nick Mears to finish the inning. Brewers manager Pat Murphy later confirmed that while the injury looked concerning, it was primarily cramping, and Misiorowski felt “all good” postgame.
“Of course, I don’t want to leave like that,” Misiorowski said. “I feel like I could have kept going, but I cramped up. Stuff happens.” His teammates and coaches echoed confidence in his recovery and future, with left-hander Aaron Ashby, who also hails from Crowder College like Misiorowski, praising his preparation and readiness. Ashby took over in relief and pitched three innings to secure his third career save, though he allowed a leadoff single in the seventh inning that ended Milwaukee’s combined no-hit bid.
Misiorowski’s debut was notable not just for its on-field brilliance but also for the context surrounding his rise. Drafted 63rd overall in the 2022 MLB Draft out of Crowder College, Misiorowski quickly established himself as one of baseball’s most electric pitching prospects. His time with the Brewers’ Triple-A Nashville affiliate further highlighted his potential, where he posted a 2.13 ERA with 80 strikeouts in 63 1/3 innings and threw a 103 mph pitch, the fastest by a true starter in the majors or minors since Statcast began tracking in 2015.
Milwaukee’s decision to promote Misiorowski came as veterans Nestor Cortes and Brandon Woodruff continue their recovery from arm injuries, and right-hander Aaron Civale was shifted to the bullpen to make room in the rotation. With the Brewers and Cardinals locked in a tight NL Central race and both teams eyeing wild-card spots, Misiorowski’s emergence adds a significant boost to Milwaukee’s pitching depth.
The young pitcher’s family and friends were on hand to witness the memorable debut, including his parents, grandparents, girlfriend, and high school coach, many sporting T-shirts that read “Here for The Miz.” The atmosphere was electric as the crowd of 27,687 fans cheered Misiorowski’s every pitch, underscoring the excitement surrounding his arrival in the majors.
Despite the injury-shortened outing, Misiorowski’s performance places him among an elite group of pitchers. He is just the ninth pitcher and sixth starter since 1900 to throw five or more hitless innings in their MLB debut. His fastball velocity and pitch count at the start of the game rank him alongside notable names such as Hunter Greene, Erik Cordier, Paul Skenes, and Mason Miller, who have all thrown multiple 100 mph pitches in their debuts.
Cardinals manager Oliver Marmol acknowledged the challenge Misiorowski posed, saying, “That’s a different arm, man. He did a nice job. The velo is real. The extension is real.” Cardinals center fielder Victor Scott II also praised Misiorowski’s competitiveness and fastball, while catcher Pedro Pagés hinted at adjustments for future matchups.
After the game, Misiorowski expressed relief and excitement now that his debut was behind him. “I haven’t slept for probably two days,” he said. “It’s going to be nice to go home and actually sleep.” The Brewers and their fans can take comfort in knowing that the young right-hander’s injury is not expected to be serious, and his dazzling first outing suggests a bright future ahead.
As Milwaukee looks ahead to the remainder of the series against the Cardinals and the rest of the season, Misiorowski’s debut stands as a beacon of hope and excitement. The Brewers have gained a powerful arm capable of electrifying performances, and if he can harness his control and maintain his health, the sky is the limit for this rising star.
