Many Boston Red Sox fans were surprised to hear Marcelo Mayer's name come up in trade conversations over the offseason, mostly for players like Ketel Marte. Half a year later, the Red Sox pulled the trigger on a trade for a very different kind of player.
Boston is expected to trade Mayer to the San Francisco Giants in exchange for reliever Erik Miller, first reported by MLB insider Ken Rosenthal of The Athletic. According to Jeff Passan, the deal is pending a medical evaluation.
A year or two ago, it was unfathomable to believe that the Red Sox would trade Mayer, — especially for a reliever — but Craig Breslow has gone big at this trade deadline. He's traded five of Boston's six most recent first-round picks since he took over as chief baseball officer.
Miller, a 28-year-old lefty out of Stanford, was selected by the Philadelphia Phillies in the fourth round of the 2019 MLB Draft. He's been an excellent late-inning arm for the Giants this season, to the tune of a 2.76 ERA, 45 strikeouts and 22 walks over 32.2 innings. He's clocked 12.4 strikeouts per nine innings and righties are batting just .183 against him this year.
Red Sox deal former top prospect Marcelo Mayer to the Giants for reliever Erik Miller
The Red Sox could use the depth at the back of their bullpen following recent reports that Garrett Whitlock is "beat up," in interim manager Chad Tracy's words, because he's been pitching so much. Jovani Morán and Greg Weissert have 45 and 43.2 innings, respectively on their arms this season and Miller will lighten their workload.
Mayer's adjustment to the major league has not gone as well as the Red Sox hoped. They promoted him for his major league debut following an injury to Alex Bregman last season and it was clearly too soon. He's batted .223/.278/.346 in 114 games since his debut and he doesn't see righty pitching well at all, to the tune of a .215 batting average and .599 OPS.
The Red Sox made the most of Mayer's remaining value after the disappointment of his 2026 showing. Clearly, they should've given him up for Marte or a similar player when they had the chance.
Miller is under team control until the 2030 season and he'll be a weapon at the back of Boston's bullpen, setting up for Aroldis Chapman. It's a shame that Mayer's tenure with the Red Sox ended in this way, but that's just the way with prospects — some don't pan out.
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