Armed with a high-octane fastball and a deceptive delivery, right-hander William Kempner dominated in a perfect relief inning to cap a whirlwind journey from Triple-A to the majors.
MIAMI — Willian Kempner became the latest Miami Marlins rookie to make his Major League debut this week.
The right-handed reliever tossed a 1-2-3 inning, including a strikeout in the Marlins 9-7 loss against the Baltimore Orioles on Tuesday at loanDepot park. Kempner told reporters after the game that he felt his debut “went well.”
"I think the best part is that I felt really good out there,” Kempner said. “I felt like I was just being myself, and that's all I can ask for at this point in my career. I have this promise to myself that I need to be that guy out there that just doesn't care what people think. I did that (Tuesday) and I'm very happy for myself."
Kempner was the latest of a trio of Marlins to make their Major League debut this homestand. Josh Ekness pitched on Sunday and catcher Joe Mack started on Monday.
It was a sneak peak into what experiencing big league hitting would be like for Kempner, who will reportedly be sent back to Triple-A for Dax Fulton. Next to make his MLB debut, Fulton enters Wednesday with 24 strikeouts in 20 innings pitched this season with the Jumbo Shrimp.
Kempner was a low-key acquisition by the Marlins from the San Francisco Giants in January 2025 in exchange for international bonus pool money. In 103 career minor league games, Kempner has 218 strikeouts in 154.2 innings pitched.
Marlins manager Clayton McCullough told reporters before the game that he thought Kempner would “be a tough look for hitters,” and that “his ability to fill up the strike zone consistently” would be to key to how his debut went.
“It’s a big fastball with movement both ways, and he has a very good breaking ball,” McCullough said. “We know he has the ability to miss bats. He’s shown that in Triple-A”
Despite being a reliever, Kempner is second among Jacksonville pitchers in strikeouts with 34, leading to a 19.96 K/9 and a 47.9 percent strikeout rate that ranks second in the International League. His most recent minor league appearance saw him striking out two batters in two no-hit innings. On the other side, Kempner had posted a 6.46 ERA and a 4.15 FIP prior to his call-up due to control issues.
Although his time with the Marlins has been brief, one never forgets their first call-up story and the realization of their dream becoming a big leaguer turning into reality. Kempner said before the game his call-up moment came in a form of a prank.
“I was on the phone with my pitching coach [Jerad Eickhoff]. I missed his call, and then I called him back, and he told me to come in and throw a bullpen tomorrow. Then he said he was just messing with me and that I was going to the big leagues. There’s no one I’d rather get that call from than him and our manager, (David Carpenter). Two amazing dudes.”
The Marlins continue to shuffle relievers to keep their bullpen fresh in a long stretch that has them playing 26 games in 27 days.
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