The Boston Red Sox head into 2026 with a major question mark at third base. After losing Alex Bregman to the Chicago Cubs in free agency and striking out on a big-name replacement, the Sox are now turning inward - and that spotlight is squarely on 21-year-old Marcelo Mayer.
Boston reportedly made a push for Bo Bichette, who’s now set to play third for the Mets, but that pursuit came up short. With no marquee addition to fill the void at the hot corner, the Red Sox are poised to give Mayer a real shot at locking down the position on Opening Day.
Mayer, the former first-round pick and once top-15 prospect in all of baseball, saw some time at third base last season - 29 games, to be exact - mostly when Bregman was sidelined. Now, with Bregman gone for good, Mayer’s opportunity just got a whole lot bigger.
The challenge? He’s still working his way back from a season-ending wrist injury that cut his rookie campaign short in July. But if you ask him, he’s ready.
“I feel good,” Mayer said this week. “I’m pretty much doing full baseball activities like a normal ramp-up. I feel like I’m in a good spot.”
That’s exactly what Boston needs to hear. Because if Bregman were still around, Mayer likely would’ve slotted in at second base, possibly in a utility role. Instead, he’s now in line to be the everyday third baseman - a significant leap, especially for a young player still finding his footing at the plate.
Defensively, Mayer showed promise. He posted a +2 Outs Above Average at third base - a solid mark that suggests he can handle the position.
Offensively, though, the numbers were more modest. In 44 games, he posted a .674 OPS, with just four home runs.
But there’s reason to believe more is coming.
Mayer reportedly added 10 pounds of muscle this offseason, a move the Red Sox encouraged in hopes of unlocking more power at the plate. That added strength could be the difference-maker in turning hard contact into extra-base hits - something Boston’s lineup could sorely use.
“My goal right now is just to get to spring training in the best shape I can and go out there and perform,” Mayer said. “You’re in the big leagues now.
For me the real work starts now. I’ve definitely gotten after it this offseason.
You learn from experience what you need to work on.”
That mindset - mature, focused, and grounded - is exactly what you want to hear from a young player on the cusp of a breakout. And while injuries have slowed his development (he’s yet to play more than 91 games in a single season in the Red Sox organization), the flashes have been there.
Before the wrist injury, Mayer was starting to turn a corner at the plate. Over his final 15 games, he slashed .262/.295/.357 - a noticeable improvement from the .212 average he posted in his first 29 games. The power still wasn’t quite there, but the contact was better, and the approach looked more confident.
In the minors, Mayer’s career high in home runs was 13. That’s not eye-popping, but it’s enough to suggest there’s some pop in the bat - especially now with the added weight and a full offseason of work under his belt.
The Red Sox are betting on Mayer’s upside, and given their lack of external reinforcements, they don’t have much of a choice. But this isn’t just about filling a roster spot - it’s about developing a cornerstone.
Mayer was drafted to be a foundational piece of Boston’s future. Now, he has the chance to prove he’s ready to be that guy.
Third base at Fenway has a new face. And if Mayer stays healthy and continues to grow at the plate, the Red Sox might just have their long-term answer already in-house.