Boston Red Sox
Mayer couldn’t put it all together after establishing himself as a blue-chip prospect with Boston.
Marcelo Mayer couldn’t live up to his potential as a former top prospect in baseball. (AP Photo/Mark Stockwell)
August 3, 2026 | 6:06 PM
2 minutes to read
The Red Sox are reportedly moving on from one of their former top prospects.
According to Ken Rosenthal of The Athletic, the Red Sox are trading shortstop Marcelo Mayer to the San Francisco Giants in exchange for lefty reliever Erik Miller.
Monday’s trade — the third of the day for Boston after deals for both Adley Rutschman and Eli White — marks the end of Mayer’s once-promising tenure in Boston.
Mayer, selected fourth overall in the 2021 MLB Draft, was once expected to be Boston’s long-term fixture at shortstop — projecting as an athletic, do-it-all infielder with a strong glove and a promising hit tool.
But Mayer could seemingly never put it all together, with the 23-year-old shortstop’s promise and standing as a premier blue-chip prospect undercut by concerns over his durability and offensive capabilities at the big league level.
Mayer — who had several promising seasons in the minor leagues cut short due to injury — ultimately only played 114 total games with Boston across parts of two seasons. During that stretch, he batted .223 with seven home runs and 32 RBI.
Injuries sprouted up once again for Mayer this season, with the former top prospect sidelined since June 25 due to a bone stress reaction in his left forearm.
Given both Boston’s reported pursuit of several shortstops ahead of Monday’s trade deadline — coupled with 20-year-old shortstop Franklin Arias’ rapid ascension as Boston’s top prospect — the writing was on the wall that the Red Sox were ready to move on from Mayer, who could make the most of a clean slate in the Bay Area.
If healthy, Mayer will make his return to Fenway Park — alongside Rafael Devers — when the Giants take on the Red Sox on August 21-23.
Moving on from a flawed, but still young, prospect like Mayer represents a risk for Craig Breslow and his staff. But Boston did add a lively arm for an already stout bullpen in Miller.
Miller, 28, is an imposing power pitcher with a 6-foot-5, 240-pound frame and plenty of swing-and-miss stuff. The lefty made 38 appearances (32.2 innings) with the Giants this season, sporting a 2.76 ERA with a 1.38 WHIP, 45 strikeouts and 22 walks.
Miller’s command will need to be fine-tuned moving forward. But his Baseball Savant page showcases plenty of upside — boasting an average fastball velocity of 96.9 miles per hour, while his whiff percentage of 34.8 percent ranks in the 97th percentile of pitchers this year.
Miller, who is under team control through the end of the 2029 season, should factor into Boston’s late-inning relief corps alongside Aroldis Chapman, Tyron Guerrero and Garrett Whitlock — giving the Red Sox another promising bullpen arm moving forward.
Conor Ryan is a staff writer covering the Bruins, Celtics, Patriots, and Red Sox for Boston.com, a role he has held since 2023.
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