BOSTON -- In the eight years since the Boston Red Sox last won the World Series, fans have been sold on a more sustainable future. A future built on the backs of homegrown talent rather than major free agent signings that have propelled the Boston teams of the past. One of the biggest pieces of that sustainable future was the 2021 fourth-overall pick, shortstop Marcelo Mayer. Now in his first full season in the big leagues, Mayer has yet to live up to the lofty expectations placed on him by both fans and the franchise alike. Is it time to be concerned about the 23-year-old infielder? 

It has been a month to forget for Mayer, who has been one of the worst hitters in baseball in May. Through 21 games in the month, Mayer is hitting just .164, a mark that is tied for the seventh-lowest among all qualified hitters. His OPS of .428 and weighted runs created+ (wRC+) of 17 rank him as the second-worst hitter in baseball for the month. Overall, he is hitting just .211 with an OPS of .570, and with an OPS+ of 58 the middle infielder has been 42 percent worse than the average major league hitter. 

Mayer's month is in some ways comparable to fellow highly touted prospect Kristian Campbell's performance in May 2025. Campbell hit just .113 in the first 26 days of the month last season, and, like Mayer, found himself as one of the worst hitters in the sport for the month. 

There is, however, one key difference between the two: defense. Campbell's struggles extended far beyond his performance at the plate, as he was one of the worst defenders in baseball during his two-month stay in Boston. In just 67 games, the then-22-year-old racked up an outs-above-average of negative nine, ranking in the third percentile. 

Mayer, however, has been more than impressive in the field. His defensive runs saved of two have him tied for the eighth-best among all qualified second basemen, while his two outs above average have him ranked just outside of the top 10 at No. 11. 

Throughout his short major league career, Mayer has struggled immensely against off-speed pitches. In 92 games played at the major league level, Mayer is hitting just .157 against changeups, curveballs, sliders, splitters, and knuckle curves, striking out 38.8 percent of the time. That's a stark difference from the .279 batting average with a 14 percent strikeout rate when he sees a four-seam fastball, cutter, or sinker.

In 2026, however, it has been the changeup specifically that has been Mayer's Achilles heel. The 23-year-old is hitless in 24 at-bats against the change, striking out a staggering 41.7 percent of the time. In his career, Mayer has just one hit against the change in 42 at-bats, good for a .028 batting average. 

Mayer spoke about his offensive struggles with the Boston Globe's Alex Speier, saying, "Obviously, it hasn’t gone the way that I wanted offensively so far, but it’s early". Despite the slow start, Mayer is confident he can turn things around. "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."

While Mayer's struggles against off-speed pitches are certainly concerning, development in baseball isn't always linear. Take longtime Red Sox shortstop Xander Bogaerts as an example: In his first full major league season in 2014, Bogaerts hit just .146 against sliders, striking out almost 40 percent of the time. The following season, he broke out in a big way, hitting .315 against the pitch. 

Mayer also has the comfort of knowing he can sort out his struggles at the big league level. Thanks to his strong defensive play, the hernia surgery that will keep Trevor Story out for nearly two months means that he is unlikely to suffer the same fate as Campbell in 2025. 

For now, though, fans will have to be patient with the young infielder as he continues to adjust to the major league level. 

Mayer will bat eighth and play shortstop on Wednesday night as the Red Sox look to snap a four-game losing streak when they take on the Atlanta Braves in game two of a three-game set at Fenway Park. Connelly Early (4-2, 3.33 ERA) will get the start for Boston, opposite Bryce Elder (4-2, 1.97 ERA) for Atlanta. First pitch set for 6:45 p.m. ET. 

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