Marlins Prank William Kempner Before He Learns of MLB Call-Up

The new Miami Marlins reliever got a dose of a prank before he learned he would be heading the Majors to join the team.

Jacksonville Jumbo Shrimp pitcher William Kempner. | Corey Perrine/Florida Times-Union / USA TODAY NETWORK via Imagn Images

William Kempner was on the phone when he found out that he was heading to the Miami Marlins. The coaching staff had a bit of fun first.

He was on the phone with Triple-A Jacksonville pitching coach Jerad Eickhoff when his manager, David Carpenter, tried to break in. Eickhoff and Kempner kept talking and once they were done talking Kempner called Carpenter back. Carpenter told him to come in to throw a bullpen.

Kempner was taken aback a bit but agreed. Then, he let Kempner know the good news.

“I got pranked,” he said to reporters in front of his locker in a video interview at MLB.com.

But, the rookie was blown away by the opportunity.

“A lot of emotions you know?” he said of finding out he was heading to The Show. “Trying to get people out here and such It’s surreal and I'm really, really pumped to get after it.”

He could pitch as early as Tuesday’s game. He took the roster spot of Chris Paddack, who was designated for assignment.

 William Kempner on What’s Next

Gonzaga pitcher William Kempner. | BRIAN HAYES / STATESMAN JOURNAL via Imagn Content Services, LLC

Kempner said that he already knows what he must improve if he wants to stay in the Majors for the long-term.

“Lower the walk rate, obviously,” he said.  “I get a little erratic sometimes. I’m working on it. But if you get some strikeouts with the walks, then we're going to be OK. I just have to do that and kind of hone in and focus on the mental game and it’s been working so far.”

With Jacksonville this season he’s 0-3 with a 6.46 ERA in 12 games. He’s struck out 34 and walked 11 in 15.1 innings.

Kempner was the San Francisco Giants’ third-round pick in the 2022 MLB draft out of Gonzaga. He spent 2022 and 2023 in the Giants’ organization but missed the 2024 season due to an injury. Before he returned to the field in 2025, The Giants traded him to Miami Marlins for international bonus pool money.

The Marlins assigned him to High-A Beloit, but he quickly worked his way up to Double-A Pensacola and Triple-A Jacksonville. Combined he was highly effective, as he went 7-3 with a 2.26 ERA in 48 appearances, all in relief. He also recorded seven saves in seven chances. He struck out 95 and walked 40 in 67.2 innings, nearly his same workload in 2023 when he went 4-5 with a 3.73 ERA in 38 games. He struck out 78 and walked 30 in 62.2 innings.