The Boston Red Sox are calling up infielder Marcelo Mayer, the No. 6 prospect in baseball and a central part of their future who they hope can play a role in their push for a postseason berth this year, sources told ESPN.
The 22-year-old Mayer, who has excelled at shortstop as he ascended through the Red Sox's farm system after they took him with the No. 4 overall pick in the 2021 draft, is likely to get playing time with All-Star third baseman Alex Bregman expected to land on the injured list after leaving Friday's game with right quadriceps tightness.
At Triple-A Worcester, where Mayer was hitting .271/.347/.471 with nine home runs and 43 RBIs in 43 games, he played four games at third base. Mayer also could see time at shortstop, with Trevor Story in a profound monthlong slump.
The arrival of Mayer marks the second of Boston's big three prospects, with Kristian Campbell earning the second-base job in spring training. After a hot start, Campbell has slumped likewise and is hitting .225/.321/.369. The third of the group, outfielder Roman Anthony, is the No. 1 prospect in MLB, according to ESPN's Kiley McDaniel, and is hitting .323/.455/.513 with six home runs and 18 RBIs at Triple-A.
The loss of Bregman, who is hitting .299/.385/.553 in his first year with the Red Sox, takes an MVP-caliber bat out of a lineup that has struggled. The Red Sox lost first baseman Triston Casas for the season to a ruptured tendon in his left knee and have struggled to find a productive fill-in, amplifying calls for the team to reach into its significant minor league depth.
Boston has taken Mayer's development slowly, with injuries limiting him to 91 games in 2022, 78 games in 2023 and 77 games last year. He is a career .273/.360/.466 hitter in 315 minor league games and projects to be a middle-of-the-order bat and Boston's long-term solution at shortstop.
Bregman's contract includes an opt-out after the 2025 season, opening the possibility of a shift to third for Mayer. At 6-foor-3 and 190 pounds, he has both the size and the arm strength typically sought for the position. But his glove at shortstop is regarded as above-average, and Boston could opt to move Story off the position for Mayer or Ceddanne Rafaela, who also plays center field for the Red Sox.
