Arguably the most shocking move of the Boston Red Sox's trade deadline was the deal for former San Francisco Giants reliever Erik Miller. He cost Boston its former top prospect and one-time shortstop of the future, Marcelo Mayer.
The deal came months after the team refused to give him up for Arizona Diamondbacks second baseman Ketel Marte (a good move, in retrospect). Boston obviously saw something in Mayer's game that pushed it to move on — it could've been the early returns on his time in the big leagues, as he produced only a .220/.282/.312 slash line over 70 games during the 2026 season.
But another concern likely lingered, which reared its ugly head twice over his major league tenure with the Sox. Mayer has been described as "injury prone" throughout his time in the minor leagues and past his promotion, a title to which he's lived up.
Mayer had been on the injured list for over a month with a forearm when the Red Sox traded him to the Giants, and it doesn't appear he'll be coming off any time soon, despite beginning a rehab assignment on August 13. John Pavlovic of NBC Sports Bay Area reported on August 21 that the Giants paused Mayer's rehab due to a flare-up of a bone bruise he had on his foot from a prior injury. As of August 24, Mayer still hadn't played in any more rehab games.
Another lingering injury has lengthened Marcelo Mayer's rehab with Giants, validating Red Sox trade
Even in the years before his promotion, Mayer struggled to make it through a season due to his frequent injuries. He never played more than 91 games in a single season, a feat he last accomplished back in 2022. He's been on the IL at least one time in all but one of his five professional seasons. The one was his 2021 debut year with the Florida Complex League when he played just 26 games. The lack of playing time has hurt his development, possibly altering the course of his career.
As Mayer continues his disappointing IL pattern, Miller has thrived in Boston. He hasn't allowed an earned run on seven hits, 15 strikeouts and three walks over 9.1 innings so far.
The Red Sox long billed Mayer as a member of their future core, and it was strange to see him moved for a reliever, as dominant has Miller has been. Mayer is still young and has years of his career to prove himself as a sustainable big leaguer, but the Red Sox were seemingly right to move on from him to get a key player for their playoff chase who is also under team control for years after.
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