Many MLB clubs, early on in spring training, start to get a good look at wide open positions and see who the standouts are at their positions, and ican often lead to dilemmas on who to start. For the Boston Red Sox, there could be an argument for the outfield, although manager Alex Cora seems to have a plan to make it work. A major concern at the moment is the left-handed pitching in the bullpen, although that could be taken care of later. But the big talk around Red Sox camp currently surrounds former top prospect Marcelo Mayer.
Jun 18, 2025; Seattle, Washington, USA; Boston Red Sox third baseman Marcelo Mayer (39) throws to first base for an out against the Seattle Mariners during the eighth inning at T-Mobile Park. Mandatory Credit: Joe Nicholson-Imagn Images
Originally, all signs pointed to Mayer being a future star in the infield at a permanent spot. He was part of the “Core 4” along with teammates Roman Anthony, Kristian Campbell, and former teammate Kyle Teel. But when he came up, the former shortstop was moved to third base when Alex Bregman went down. Splitting time with Abraham Toro, offensively, Mayer had a disappointing slash line of .228/.272/.402 in 44 games. Defensively, though, he did fine. He had two errors in 308 2/3 innings across second, third, and shortstop.
Does Marcelo Mayer Fit on the Red Sox Roster?
Recently, however, there have been questions about Mayer’s spot, to the extent that his making the Opening Day roster is up for debate. Now, these questions are not his fault. After all, he was just a rookie last year and just turned 23 in December. But, given the departure of Bregman and also the uncertainty of who the second baseman would be, Boston invested some money into the infield, acquiring Caleb Durbin and Andruw Monasterio in trades, and signing Isiah-Kiner Falefa. These players joined a group that included Campbell and the injured Romy Gonzalez. Now, while Durbin is projected to start at third, and Gonzalez is more seen as a utility guy who mainly plays second, there’s still good competition.
The Newcomers
Andruw Monasterio
When looking at the stats side by side, Monasterio is actually a perfect player to compare against, seeing as they had a similar amount of plate appearances despite Monasterio playing in 24 more games. Hitting-wise, they were pretty similar, both hit four home runs (and 14 extra base hits), and were within 5 or 6 of each other for hits and RBI. Mayer had one more walk as well. But when you get into the averages, it’s clear where the separation is.
Mayer’s slash line: .228/.272/.402
Monasterio’s slash line: .270/.355/.437
Going into the analytics, Mayer has a .301 batting average when putting the ball in play. It’s still less than the newcomer’s .333, but it’s not bad. The main separation is at the strikeout rate. They’re both relatively high, but Monasterio (23.7%) is far more patient and eagle-eyed than Mayer (30.1%)
Isiah Kiner-Falefa
Although Kiner-Falefa is not the best hitter, he still has a noticeably better average than Mayer at .262. The only edge Mayer’s got on him is power, and that’s not saying much. However, Kiner Falefa may not get a chance to start the whole season, and maybe he and Trevor Story could mentor Mayer, as Bregman did with the younger players last season. Fielding-wise, Kiner-Falefa is the clearly better player, but he’s got a Gold Glove, so that’s a given.
The Teammate
Kristian Campbell
Now granted, all these guys are teammates, but given that Mayer and Campbell have played together much longer and they both came up last year, he’s in a different category than the other two. The fact that Campbell won Rookie of the Month in April and finished with a worse average by June shows how much he’s struggled. Despite this, Campbell finished the season with a .319 OBP. He also had a significantly higher walk rate at 11%. Offensively, he may have started hot. But defensively, he was a liability. He had seven errors at second and had a -16 DRS in nearly 472 innings. For comparison, Mayer was -1 in 57 innings at second last season. Both were hyped up coming into the 2025 season, but at least Mayer’s glove kept him up in Boston.
Will Mayer Make The Roster?
So now the key question: with how good Monasterio has been and with Gonzalez coming back at some point, does Mayer have a spot on this roster? In all honesty, yes, he does. In terms of last year, he didn’t struggle any more than Campbell did, and actually did better defensively. And as for newcomers, there’s a world where Kiner-Falefa moves to backup Durbin at third and all three of them make the roster.
Incoming dinger from Marcelo Mayer pic.twitter.com/14UXs2eWik
— Dillard Barnhart (@BarnHasSpoken2) February 27, 2026
On Friday against the Atlanta Braves, the Red Sox may have gotten blown out, but Mayer made his debut. In that debut, he went one for three with a 381-foot homer. Mayer’s not going away during the World Baseball Classic, so he’s got more time to prove his worth on the roster. He should be on the roster come March 26th.
Main Photo Credit: © WooSox Photo/Ashley Green / USA TODAY NETWORK via Imagn Images