Why Marlins top catching prospect Joe Mack isn't being called up yet

The Miami Marlins traded Nick Fortes to the Tampa Bay Rays on Tuesday morning. This season—his fifth at the major league level—Fortes was more or less performing to the standard that the Marlins have grown accustomed to. However, the 28-year-old catcher became expendable as younger alternatives at the catcher position with higher offensive ceilings come up behind him. That's a good problem to have. 

Acquired via the Rule 5 Draft, Liam Hicks has made a surprisingly positive impact. He's got a Fortes-like aptitude for blocking pitches in the dirt to go along with a sophisticated plate approach. The left-handed-hitting Canadian has accrued 0.7 fWAR in 72 games.

Fellow rookie Agustín Ramírez received his initial call-up when Fortes was on the injured list and immediately demonstrated that he's a legitimate power threat. It left the Marlins no choice but to simultaneously roster all three catchers.

Realistically, Ramírez's future is not behind the plate. Monday's game in St. Louis happened to be one of his sloppiest defensive efforts, including errors for an errant throw and catcher interference. A handful of replies to the Fish On First Twitter account fumed about it, pleading for Joe Mack to be called up.

Even more so than Hicks or Ramírez, Mack's progression is most responsible for pushing Fortes out the door. Drafted by the Marlins in 2021, he enjoyed a breakout campaign in 2024, leading all Miami minor leaguers in home runs while winning the MiLB Gold Glove at his position. He earned a promotion to Triple-A Jacksonville in April of this year and continues to thrive on defense. Mack was a slam-dunk selection to represent the Marlins at the Futures Game in Atlanta.

In 2025, Mack is slashing .258/.335/.436 with a 112 wRC+ through his first 78 games played. With only a handful of exceptions, he's younger than every pitcher he has faced. Fish On First ranks him second among Marlins prospects behind only Thomas White.

With the Fortes trade now official, will we see Mack selected to the roster as the corresponding move? No, and here's why.

The 22-year-old could have made it a tougher decision by going on a heater following the Futures Game. Instead, it's been the opposite—Mack is scuffling with the bat lately. In seven games post-All-Star break, he has posted a .115/.179/.192 slash line with an egregious 57.1% strikeout rate. Almost all of those strikeouts have been whiffs against non-fastballs. There's no sense in exposing him to the big leagues until he gets back to tracking balls more clearly out of the pitcher's hand.

As a consensus Top 100 MLB prospect, Mack is a prime candidate for MLB's Prospect Promotion Incentive (PPI). The name is ironic because in this case, it actually behooves the Marlins to preserve his rookie eligibility for 2026 instead of calling him up now. If Mack spends a full year in the majors next season and wins National League Rookie of the Year, the Marlins would receive a compensatory pick after the first round of the 2027 draft (plus the millions of dollars in bonus pool money associated with that pick).

Mack will still be ROY-eligible next season if he spends 45 days or fewer on the Marlins active roster this season. Waiting until August 15 for a call-up would thread that needle.

It isn't a lock that Mack debuts in 2025, to be clear. He must first bust out of his mini-slump. Then, the Marlins have to decide whether to abandon the Agustín Ramírez catching experiment, or zag the other way and maximize his reps down the stretch just in case something clicks.

Mack is not yet on the club's 40-man roster. He will need to be selected by mid-November to protect him from the upcoming Rule 5 Draft. Perhaps the Marlins want to kick that can down the road as far as possible to give themselves flexibility for other transactions.

Without being hyperbolic, Mack has the potential to be the best catcher to play for the Marlins since J.T. Realmuto. Just have a little patience with him.

Interested in learning more about the Miami Marlins' top prospects? Check out our comprehensive top prospects list that includes up-to-date stats, articles and videos about every prospect, scouting reports, and more!