The Marlins placed Kempner on the 15-day injured list Sunday due to a right elbow sprain.
Kempner was called upon to pitch Thursday against Seattle and Saturday versus Cleveland and struggled in both games, allowing four runs on five hits with three strikeouts and two walks over 2.1 innings. He'll now be sidelined until at least July 27.
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Marlins' William Kempner: Recalled from Triple-A
Rotowire
The Marlins recalled Kempner from Triple-A Jacksonville on Friday, Christina De Nicola of MLB.com reports.
Kempner was sent down last month despite logging nine scoreless innings with a 10:2 K:BB in six relief appearances. The 25-year-old will likely fill a middle relief role, but his stay in the majors could be brief as the Marlins will need a spot next week for a fifth starter, expected to be Janson Junk (shin).
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Marlins' William Kempner: Returns to Triple-A
Rotowire
Kempner was optioned to Triple-A Jacksonville on Tuesday.
The right-hander fired 2.1 scoreless innings Monday against the Phillies and is being sent down Tuesday in favor of a fresh bullpen arm (Dax Fulton). Kempner has given up just three hits with a 10:2 K:BB across nine scoreless frames in the majors this season, so it should only be a matter of time before he gets another look with the big club.
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Marlins' William Kempner: Nabs first big-league win
Rotowire
Kempner (1-0) picked up the win Wednesday, walking two and striking out three over two scoreless, no-hit innings of relief in a victory over the Diamondbacks.
The rookie right-hander took the mound in the seventh inning, the third of four Miami pitchers in a combined shutout, and he wound up being credited with the win. Kempner has yet to allow a run in his first five big-league appearances, posting a 0.75 WHIP and 8:2 K:BB over 6.2 innings, but he doesn't yet appear to be part of the high-leverage picture for manager Clayton McCullough -- he entered Wednesday's contest with the Marlins already up 8-0.
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Marlins' William Kempner: Recalled from Triple-A
Rotowire
The Marlins recalled Kempner from Triple-A Jacksonville on Tuesday, Christina De Nicola of MLB.com reports.
He's grabbing the roster spot vacated by Chris Paddack, who was designated for assignment. Kempner holds a 6.46 ERA this season with Jacksonville but has struck out a whopping 34 batters over 15.1 innings. He will be making his major-league debut when/if he enters a game.
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Marlins' William Kempner: Sent to Triple-A
Rotowire
The Marlins optioned Kempner to Triple-A Jacksonville on Sunday.
Kempner was added to Miami's 40-man roster in November but was never a likely bet to crack the Opening Day roster. The 24-year-old had a quality showing in his first taste of Triple-A last year with a 2.65 ERA, 1.35 WHIP and 25:15 K:BB over 17 innings, and he could make his MLB debut at some point in 2026 if he continues to pitch well for Jacksonville.
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Marlins' William Kempner: Joins 40-man roster
Rotowire
The Marlins selected Kempner's contract from Triple-A Jacksonville on Tuesday.
Kempner was acquired from the Giants last winter in exchange for international bonus pool space, and the Marlins won't leave him exposed to potentially being selected during the upcoming Rule 5 Draft. Across three minor-league levels in 2025, the 24-year-old pitched to a 2.26 ERA, 1.15 WHIP and 95:40 K:BB over 67.2 innings.
