One year into his big league career, the Red Sox’ Marcelo Mayer remains a work in progress

Sunday marked a two-fold milestone for Marcelo Mayer. On the one-year anniversary of his big league debut, he made his first career big league start at shortstop.

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What does Mayer remember of his callup between games of a doubleheader on May 24, 2025, when Alex Bregman’s placement on the injured list prompted a scramble from Worcester to Boston?

“That was definitely a special day, but it honestly didn’t feel like my debut, because that day was so crazy,” recalled Mayer. “I had, like, 30 minutes to get ready for my first big league game. I didn’t even know where my shoes were five minutes before the game, I didn’t have a locker because it wasn’t ready. I was in the middle of the clubhouse, scrambling for my stuff, which I guess helped with the nerves.

“Time has definitely flown by, I feel like, since that [debut].”

Yet during that year, progress has been deliberate. Mayer remains a player looking to live up to not only the hype and potential that came with being taken as the No. 4 pick in the 2021 draft, but his own expectations.

“I have the highest standards for myself I possibly can. Whatever people’s standards are of me, mine are higher — trust me,” said Mayer. “As players, as athletes, we all want to perform to the best level that we’re capable of, and that we know we can. When you’re not [doing that], it gets frustrating.”

Defensively, he’s made an exceptional transition to the big leagues. Though he’d spent the majority of his amateur and minor league careers at short, he looked like a hand-in-glove fit at third base in 2025 and second base through two months of 2026. He’s an asset in the field, part of why the Sox feel comfortable with him at shortstop in Trevor Story’s absence.

Mayer takes pride in supporting his pitchers with his glove, but is dissatisfied with his performance as a hitter. He finished Sunday hitting .214/.277/.300 in 2026, and .221/.275/.348 in 91 career games. He’s been one of the least productive regulars in baseball.

“Obviously, I want to hit better,” said Mayer. “I’ve always prided myself on hitting, and I feel like people right now know me as a defense-first guy, when that’s not really who I’ve ever been. My defense has just been that much better than my bat, and that’s what people see.”

People — including other teams — see vulnerabilities. Though Mayer has demonstrated solid swing decisions, he’s also had glaring holes.

He’s 1 for 35 since his callup on changeups, a .029 average that is the worst in the big leagues. He’s 2 for 34 on “shadow zone” pitches near or just below the bottom of the strike zone, including 1 for 19 this season. (That hit came Sunday, when he ripped a slider for an RBI single in a 6-5 loss to the Twins.)

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Pitchers are well aware of those struggles. Of the 227 batters who entered Sunday having seen at least 500 pitches, the 28 percent usage of offspeed pitches (changeups and splitters) against Mayer was the highest of any hitter. The 18 percent rate of pitches in the shadow zone along the bottom edge of the plate ranked 22nd.

Mayer knows those deficiencies and is working to close his holes.

“Obviously, it hasn’t gone the way that I wanted offensively so far, but it’s early,” said Mayer. “We all want to be really good right [away]. But looking back in my [minor league] career, I’ve always struggled going up to new levels.

“The biggest thing is just not making a big deal out of it, and trusting myself as a hitter, because it’s not my first rodeo struggling in a new level. I feel like I still don’t have that many at-bats. I’m approaching a year, but at the same time, I don’t have a year’s worth of at-bats. The biggest thing is just learning with every single at-bat.”

There are no guarantees what Mayer will become. Numerous standout prospects never lived up to their hype. But many struggled toward the beginning of their careers before establishing themselves.

As such, the Sox remain mindful of what Mayer might become. His minor league track record of line-to-line extra-base hits and elite bat speed suggest power potential that would be difference-making in a lineup short on thump.

But while the Sox remain optimistic those abilities will emerge in the big leagues, they know Mayer’s path to improvement doesn’t follow a set schedule.

“You can see this guy hitting 20 [homers] at some point in his career, and it’s not just one year that this guy’s capable of [doing that],” said interim third base coach Chad Epperson, who managed Mayer in Double-A in 2023-24. “I just think he’s still in that growing stage of, what’s the game telling me what to do and what do I need to do? Sometimes he just wants to force the issue.

“Would it be nice for him to be the Marcelo we know? Yeah, but that’s [going to happen] in time, in time.”.

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