Jacob Misiorwoski ties career worst against the Cubs. What happened

Jacob Misiorowski walked off the mound at Wrigley Field on Wednesday, Sept. 2 having thrown 92 pitches, recorded 12 outs, and allowed five earned runs. In just four innings, the Milwaukee Brewers ace had tied his career high for earned runs allowed and had one of the worst starts of his career. The Brewers bullpen and bats pulled out a 9-5 win over the Chicago Cubs, so Misiorowski’s struggled will be overlooked.

But, five earned runs ties his career worst.

On July 2, 2025, when the New York Mets got him for five in just 3⅔ innings, his fourth big-league start and his first career loss. So it’s not exactly unprecedented. What makes it worth digging into is the why, and the Statcast readout from Wednesday night is not the story you’d guess.

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Milwaukee Brewers catcher Gary Sanchez wears a special chest protector to commemorate Jackie Robinson Day during the game against the Toronto Blue Jays at American Family Field on April 15, 2026.

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The Pittsburgh Pirates’ Konnor Griffin celebrates with a traffic cone after making his major-league debut in a 5-4 defeat of the Baltimore Orioles at PNC Park on April 3, 2026.

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Cleveland Guardians players warm up as the launch of NASA’s Artemis II is shown on the center-field video board at Dodger Stadium on April 1, 2026.

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Two F-35C planes from Air Test and Evaluation Squadron NINE Detachment Edwards Air Force Base perform a flyover before the Opening Day game between the Arizona Diamondbacks and Los Angeles Dodgers at Dodger Stadium on March 26, 2026.

Everyone’s first instinct watching this is going to be fatigue. That’s been the storyline all summer. But look at the actual velocity readings and that theory doesn’t hold up, not for Wednesday anyway. His fastball averaged 100.9 mph, a shade above his season average of 100.6, and it never wavered: 100.9, 101.0, 100.5, 100.5, inning by inning. He touched 102.4. Five pitches sat at 102 or better. That’s not a tired arm by any measure.

So what happened? He stopped throwing his fastball. Just 48% usage Wednesday, way down from his usual 64%. He leaned heavily on his cutter (36%), nearly triple his normal 14%. And on the fastballs he did throw, he found the zone only 39% of the time, which led to four walks. Hitters weren’t catching up to diminished stuff, he racked up 13 swinging strikes on the night to go with his five punchouts. He had the same power arm he always has. He just didn’t use it much, and when he did, he couldn’t find the plate.

That’s actually a different problem than the one everyone is watching.

Against Atlanta on Aug. 21, the fastball was “100-101, a tick down,” in Trevor Megill’s words and Misiorowski leaned on his offspeed stuff to cover for it. Pat Murphy admitted “there could be some fatigue involved here.” Six days later against the Mets, his four-seam averaged 98.7, nearly two ticks off normal, and Misiorowski chalked it up to the calendar: “The body’s tired. Everyone’s tired. It’s August going into September.” Both nights, though, the results stayed clean, so nobody made much of it.

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Misiorowski is 24, in his first full big-league season, and he’s already up to 155 innings. That’s more than his entire 2025, majors and minors combined, roughly 129⅓, with a month still to go. He’s thrown more than 2,000 pitches, nearly double his rookie-year total. He’s 42 strikeouts from Ben Sheets’ single-season franchise record of 264. Every one of these starts carries more weight than the last, both for him individually and for a Brewers team chasing a No. 1 seed.

Milwaukee’s handling of all that has been inconsistent at best. They scratched him once in July for arm fatigue, floated a plan to shorten his outings by an inning here and there, then by mid-August basically abandoned the caution altogether. They let him go every five days with no pitch limit. That approach carried him through two starts where the warning signs were there in the pitch data and nowhere in the results.

Misiorowski threw five no-hit innings in his June 2025 debut and made the All-Star team five starts later. It is the fastest anyone’s done that in league history. Then the second half arrived and it all came apart: a 5.89 ERA over his final nine outings, bottoming out with that same five-run meltdown against the Mets.

This season, the Brewers preached smarter deployment, more oversight, no repeat of a rookie hitting a wall in September. Whether Wednesday is the first crack in that plan or just a genuinely weird one-off from a guy who clearly still has his arm depends entirely on what his next start looks like.

If the fastball usage snaps back to normal next time out, this was a strange night and nothing more.

If he keeps burying his heater in favor of the cutter and still can’t find the zone, that’s a real problem. It’s arguably a stranger one than fatigue, because it points at something mental or mechanical rather than just tired legs. Either way, the Brewers are still stuck with the question they’ve been dodging since July: how hard do you keep leaning on a 24-year-old who’s already thrown more than he ever has in his life, with October still ahead of him.