The Marlins selected catcher Joe Mack and right-handers Will Kempner and Josh White onto the 40-man roster to keep them out of the Rule 5 draft. Miami designated outfielder Joey Wiemer for assignment in a corresponding move, as they’d previously had two vacancies.
Mack is one of the more obvious names to keep away from the Rule 5 draft. A supplemental first-round pick out of high school in 2021, he has developed into one of the better all-around catching prospects in the majors. The left-handed hitter connected on 21 homers with a .257/.338/.475 slash line in 468 plate appearances between the top two minor league levels.
Most of that production came in Triple-A. Mack is on the doorstep of the majors and he’s a better defensive catcher than either Liam Hicks or Agustin Ramirez. Mack has the best chance of the group to be Miami’s long-term answer behind the plate. It’s not out of the question he breaks camp, and he’ll almost certainly debut at some point next season.
Kempner, 24, was acquired from the Giants for international bonus pool room last offseason. A third-round pick out of Gonzaga in 2022, he’s a pure reliever who turned in a 2.26 ERA across 67 2/3 innings between a trio of levels in his first season in the Miami system. Kempner fanned more than a third of opponents but walked upwards of 14% of batters faced. He sits around 95 MPH and could be an up-and-down reliever next season. The 24-year-old White should also be in that mix after running a monster 40.8% strikeout rate across 67 2/3 frames between the top two levels. The former fifth-round draftee sits in the 93-94 MPH range and leans heavily on a plus mid-80s slider.
Miami claimed Wiemer, a one-time top prospect, off waivers from Kansas City in August. He played in 27 games down the stretch, hitting .236 with a trio of home runs but striking out 23 times in 61 trips to the plate. Wiemer has big physical tools but has been too strikeout prone throughout his career. He’s a .205/.279/.359 hitter in a little under 500 plate appearances. Miami can non-tender him on Friday and try to bring him back on a minor league contract.