The Boston Red Sox completed three trades before Monday’s deadline closed. The headliner was the Adley Rutschman acquisition from Baltimore. The Eli White addition from Atlanta provided outfield depth. But the other move carried a different kind of weight.
The Red Sox sent Marcelo Mayer to the San Francisco Giants for left-handed reliever Erik Miller and outfield prospect Carlos Gutierrez.
A player who was drafted to be the franchise shortstop is now someone else’s project. That reality was not lost on the man who made the call.
Breslow Addresses the Mayer Trade
Craig Breslow did not sugarcoat the difficulty of the decision. He also did not back away from it.
“He was a really big part of this organization, someone that was looked upon to be part of a core,” Breslow said. “And I still think that’s going to happen. It’s going to happen with the San Francisco Giants at this point, but he’s an incredibly talented player.
The Red Sox selected Mayer with the fourth pick in 2021. He rose through the farm system as one of the organization’s premier prospects. His arrival at Fenway Park in May 2025 carried the weight of years of anticipation.
The expectation was that Mayer would anchor the infield for years. Breslow made clear the trade does not reflect a loss of belief in the player.
“In no way is this an indictment of Marcelo,” Breslow said. “I still think he is an incredibly talented player, and he’s going to have a very successful major league career.”
GettyBOSTON, MASSACHUSETTS – JUNE 17: Marcelo Mayer #11 of the Boston Red Sox throws to first base for an out during the third inning of a game against the Toronto Blue Jays at Fenway Park on June 17, 2026 in Boston, Massachusetts. (Photo by Brian Fluharty/Getty Images)
Breslow on the Shortstop Situation
Breslow pointed to the organization’s internal options at shortstop as part of the reasoning, citing Andruw Monasterio, the injured Isiah Kiner-Falefa and Trevor Story, and prospect Franklin Arias.
“In some ways it’s probably a credit to the player development group and the organization that we were able to make this trade and still feel like we’ve got players in-house who are able to fill a major league shortstop role,” Breslow said.
GettyPHILADELPHIA, PENNSYLVANIA – JULY 12: Franklin Arias #19 of the Boston Red Sox on the American League Team warms up at Citizens Bank Park on July 12, 2026 in Philadelphia, Pennsylvania. (Photo by Emilee Chinn/Getty Images)
What Miller Brings to the Red Sox
In Miller, the Red Sox added a left-handed arm with a 2.76 ERA across 38 appearances this season. The 28-year-old brings a 97 mph sinker and has dramatically increased his ability to generate strikeouts this year, jumping from a 17.2 percent rate last season to 31.7 percent.
He joins a late-inning group that already includes Garrett Whitlock, Justin Slaten, Tyron Guerrero, and closer Aroldis Chapman. Breslow framed the addition as a postseason necessity.
“As you think about a bullpen down the stretch and potentially into the postseason, the ability to bring guys in who can get swings and misses and shorten the game when relievers are available almost every night because of the schedule becomes really, really valuable,” Breslow said.
GettyErik Miller.
Final Word for the Red Sox
Marcelo Mayer’s chapter in Boston is over. It did not end the way anyone envisioned when his name was called on draft night. But the Red Sox are not building for five years from now. They are building for October.
Miller gives them a weapon for the stretch run. The cost was a player whose potential never fully materialized in a Red Sox uniform.
That is how the deadline works. Breslow understood that. The move says everything about where this team is now.
Red Sox Make Honest Marcelo Mayer Admission After Giants Trade