Marlins protect three prospects, including highly touted catcher, from Rule 5 draft
The Miami Marlins on Tuesday added three prospects to their 40-man roster to protect them from being selected from next month’s Rule 5 draft.
The headliner of the group: Catcher Joe Mack, who is ranked as Miami’s No. 4 prospect and the No. 70 overall prospect in baseball by MLB Pipeline.
Right-handed relief pitchers Josh White and Will Kemper were also added to the 40-man roster. Outfielder Joey Wiemer, who played 27 games for the Marlins this year, was designated for assignment to add space.
Mack, who the Marlins selected 31st overall in the 2021 MLB Draft, has turned into one of Miami’s top position player prospects the past two years. He hit .255 (224 for 880) with 52 doubles, 55 home runs and 136 RBI while playing stellar defense behind the plate. This included hitting .250 with a .779 on-base-plus-slugging mark in 99 games for the Triple A Jacksonville Jumbo Shrimp, which won the Triple A national championship this season.
White, 24, was a fifth-round pick by Miami in 2022 and had a breakout 2025 campaign. In 45 appearances across Double A Pensacola and Triple A Jacksonville, he had a 1.86 ERA with 107 strikeouts in 67 2/3 innings while holding opponents to a .166 batting average against.
Kempner, 24, posted a 7-3 record and 2.26 ERA (17 ER/67.2 IP) in 48 relief appearances between three levels (High-A Beloit, Double-A Pensacola, and Triple-A Jacksonville) in 2025. He also had 95 strikeouts while holding opponents to a .162 batting average against in his first season with the Marlins organization.
The Rule 5 Draft will be held on Dec. 10 at the end of MLB’s annual winter meetings, which this year take place in Orlando.
This story was originally published November 18, 2025 at 6:03 PM.
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