The Boston Red Sox open their 2026 season against the Cincinnati Reds on Thursday, but highly touted rookie Marcelo Mayer will not be in the starting lineup.
The Red Sox’s 2021 No. 4 overall draft pick will start on the bench because manager Alex Cora does not want the left-handed-hitting Mayer to face a left-handed pitcher, according to a report by insider Chris Cotillo of MassLive. The move raises immediate questions about how quickly Boston is willing to trust one of its top prospects.
Who Starts at Second Base for Boston on Opening Day?
Cora said Tuesday that he would likely use Mayer, in what is intended to be the 23-year-old’s first full season in the major leagues, in a platoon role this season, at least in the early going.
“Cora indicated that Mayer will sit against left-handers, with either Isiah Kiner-Falefa or Andruw Monasterio sliding in at second base against righties,” according to a CBS Sports report. “Back in February, before spring training started, Cora envisioned Mayer playing against all starters, but it appears that won’t be the case to start the season.”
When the Red Sox posted their official starting lineup to face Reds southpaw Andrew Abbott, Kiner-Falefa was listed at second base, batting seventh in an order topped by last year’s rookie sensation Roman Anthony. Designated hitter Jarren Duran, batting third, and right fielder Wilyer Abreu in the sixth spot were the only three left-handed batters in the Boston lineup.
GettyIsiah Kiner-Falefa gets the nod at second base over Marcelo Mayer on Opening Day.
Mayer Struggled Badly Against Left-Handed Pitching
The numbers behind Cora’s Meyer decision tell a more revealing story. Though Mayer’s rookie status remains intact through 2026, he was called up in May last year to fill in at third base for the injured Alex Bregman. In his short, 44-game stint with the Red Sox before going down with a wrist injury himself, Mayer failed to produce any meaningful offense against left-handed pitching.
In just 27 plate appearances, Mayer managed only a .416 OPS against lefties, striking out 10 times. One of his four hits was a triple, however, and he also drew one walk.
In his eight-year major league career, Kiner-Falefa has not exactly been a lefty killer himself, though his results have been better than Mayer’s small sample. With 957 plate appearances against southpaw pitching, Kiner-Falefa has compiled an OPS of only .643 with eight home runs.
GettyAndruw Monasterio was acquired in a trade with the Milwaukee Brewers.
Monasterio a Second Platoon Option
The Red Sox also gave a spot on the Opening Day roster to 28-year-old middle infielder Andruw Monasterio, who was acquired along with third baseman Caleb Durbin from the Milwaukee Brewers in a trade just a week before the start of spring training.
Monasterio has the best numbers against left-handers of the Red Sox second-base trio, with a .727 OPS and four home runs in 213 plate appearances.
The former Brewers infielder also put together a surprisingly impressive spring training for the Red Sox, recording 12 hits in 43 at-bats, including a home run, while striking out only nine times with five walks.
How long this arrangement lasts — and when Mayer gets his next opportunity — now becomes the key question.
Red Sox Reveal Plans For Marcelo Mayer on Opening Day