JACKSONVILLE, Fla. – Former Jacksonville Jumbo Shrimp right-handed pitcher William Kempner made his major league debut on Tuesday for the Miami Marlins in a game against the Baltimore Orioles at loanDepot Park. He is the third Jumbo Shrimp alumnus in as many days to debut in the big leagues.
The 24-year-old from San Jose, Calif., needed just eight pitches to get through a perfect eighth inning of Miami’s 9-7 loss to Baltimore. Kempner notched a strikeout, fly out and groundout in his lone inning of work.
After beginning the 2025 season with High-A Beloit, Kempner was promoted first to Double-A Pensacola, and later in the campaign, reached Jacksonville for the first time, helping the Jumbo Shrimp capture the Triple-A National Championship. In 13 games, he went 3-0 with a 2.65 ERA, yielding only eight hits in 17.0 innings while racking up 25 strikeouts. Prior to his call-up this season, Kempner had pitched in 12 games with the Jumbo Shrimp, striking out 34 in 15.1 innings pitched.
Kempner was originally selected by the San Francisco Giants in the third round of the 2022 MLB draft out of Gonzaga University. After not pitching in 2024 due to a broken foot, he was traded to the Marlins on January 15, 2025 in exchange for international bonus pool money and future considerations.
Kempner is the fifth Jacksonville alumnus to debut in the major leagues during the 2026 season, following infielder Deyvison De Los Santos (March 29, Marlins) and right-handers Matt Pushard (March 29, St. Louis Cardinals) and Josh Ekness (May 3, Marlins) and catcher Joe Mack (May 4, Marlins). A total of 1,061 players have played both for Jacksonville and in the major leagues. The history of Minor League Baseball in Jacksonville dates back to 1904.
ABOUT THE JUMBO SHRIMP: The Jacksonville Jumbo Shrimp are the Triple-A affiliate of the Miami Marlins and compete in the International League. The 2025 International League and Triple-A National Champions, the Jumbo Shrimp call VyStar Ballpark home for baseball but also a wide variety of additional community focused events with a goal of providing Affordable, Family, FUN to Northeast Florida. Winners of many marketing and sales awards and recognition since the team was rebranded prior to the 2017 season, the Jumbo Shrimp continually lead the state of Florida in attendance across all minor league professional sports organizations.