The Boston Red Sox have made yet another move as the minutes tick down to Monday's 6:00 p.m. ET trade deadline. According to Ken Rosenthal of The Athletic, the Red Sox are nearing a deal to send shortstop Marcelo Mayer to the San Francisco Giants in exchange for left-handed reliever Erik Miller. 

The hard-throwing left-hander has posted a 2.76 ERA in 32.2 innings coming out of the struggling Giants bullpen, holding batters to a .198 batting average. Miller has massive strikeout stuff, generating a 34.8 percent whiff rate and a 31.7 percent strikeout rate, while featuring a sinker that averages 96.9 mph.

Despite the massive strikeout stuff, Miller has major command problems, walking 15.5 percent of the batters he faces, the seventh-highest walk rate among all relievers with at least 30 innings of work. 

Standing 6-foot-5 and 269 lbs, Miller has a lot of the traits that the Red Sox have targeted under Chief Baseball Officer Craig Breslow, a big fastball with major extension, which ranks in the 71st percentile. 

If the Red Sox pitching lab, which has had major success with pitchers like Miller, can get the command under control, he has the makings of a major back-end bullpen piece for the Red Sox. 

The 28-year-old comes to Boston with three seasons of team control after the 2026 season, meaning he won't be a free agent until after the 2029 season. 

For Mayer, it's an unceremonious ending for a player who was thought to be the centerpiece of Boston's nearly decade-long rebuild since its last World Series title. 

Prior to landing on the injured list thanks to a stress reaction in his left forearm, Mayer was hitting only .220/.282/.312/.594 while playing both shortstop and second base. Among the 23-year-old's biggest weaknesses is his struggles with offspeed pitches, particularly changeups, where he has hit just .125 in 32 at-bats. The trip to the IL marks the second of Mayer’s short MLB career, after the former first-round pick missed the final 58 games of 2025 with a right wrist sprain.  

In 114 games at the major league level, Mayer has hit only .223/.278/.346/.625 with seven home runs and 32 RBI. 

Injuries have undoubtedly become part of Mayer's story, as he has missed time in each of his five professional seasons. Prior to his placement on the injured list due to the stress reaction, MassLive.com’s Sean McAdam reported that there were some in the Boston organization who questioned his toughness and ability to play through the “day-to-day minor physical setbacks” associated with playing a full 162-game season. 

Now, he'll look to flip the script on a disappointing start to his major league career in San Francisco. 

Update 6:30 p.m. ET. In addition to Miller, the Red Sox acquired outfield prospect Carlos Gutierrez from San Francisco in the deal for Mayer. The 21-year-old has hit .271/.385/.441/.826 in 83 games for High-A Eugene. According to MLB Pipeline, he was the No. 17 prospect in the Giants organization. 

The Red Sox are off on Monday’s trade deadline day after sweeping the defending World Series champion Los Angeles Dodgers. They’ll welcome the AL Central-leading Chicago White Sox to Fenway Park for a three-game set that gets underway on Tuesday night. Davis Martin (9-5, 3.62 ERA) will get the start for Chicago, while the Red Sox have not yet named a starter. First pitch is set for 7:10 p.m. on Tuesday night.