Scouting Report: William Kempner
Miami Marlins | RP
Overall
Summary
William Kempner, 24-year-old right-handed pitcher from Gonzaga University, was recalled by the Miami Marlins from Triple-A Jacksonville on May 5, 2026. He made his MLB debut on May 6 against Baltimore, throwing a perfect eighth inning with one strikeout on just eight pitches. The following day (May 6), he was optioned back to Jacksonville to make room for another bullpen arm. Kempner was originally drafted by San Francisco in the third round of the 2022 MLB Draft and traded to Miami in January 2025. He missed the entire 2024 season due to a broken foot but has shown exceptional strikeout potential in Triple-A with a 19.96 K/9 rate and 47.9% strikeout rate (second in IL). His main weakness is control issues, as evidenced by his 6.46 ERA in Jacksonville despite elite strikeout numbers.
Strengths
- Elite strikeout potential with 19.96 K/9 in Triple-A (34 K in 15.1 IP)
- Deceptive arm angle with nasty sweeper movement
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