“It is what it is. Take it day by day and crush the rehab,” he said.

Bregman was injured in the fifth inning of Friday’s 19-5 victory against the Orioles when he singled to left field and pulled up after rounding first base.

Initially, it was thought he had avoided a long-term injury. But Bregman described not being able to sleep because of the pain.

It’s a huge loss for the Red Sox. Bregman is hitting .299 with a .938 OPS and started 51 of the first 52 games. He leads major league third basemen in OPS, extra-base hits, bWAR (3.0), and nearly every other statistic.

“Obviously, he’s a big part of our offense. We’ve just got to find ways to score runs in a different way and we’re prepared for that,” manager Alex Cora said.

How the Red Sox are prepared to replace a player who was playing at an All-Star level is uncertain. The first move was to summon highly regarded infielder Marcelo Mayer from Triple A Worcester.

The 22-year-old hit sixth and started at third base in the second game of Saturday’s doubleheader against Baltimore. He was 0 for 4 in a 2-1 loss.

Mayer, a shortstop, played four games at third base for Worcester this season. He hit .271 with an .818 OPS in 43 games.

“We’ll probably mix and match a little more, be more aggressive in certain areas — pinch hitting, all that,” Cora said. “Nobody’s going to feel sorry for us; that’s the nature of the business. And if we feel that we are this good, and we have a chance to play in October, then you have to overcome stuff like this.”

Bregman had a .760 OPS over 32 games for the Astros when he returned from his quad strain in 2021. Houston reached the World Series and lost to the Braves in six games.

The Astros were a talent-laden powerhouse that season, winning 95 games even with Bregman’s extended absence. Abraham Toro, now with the Red Sox, was one of the players who filled in for Bregman.

As Mayer unpacked his travel bag, Bregman was wrapping up his comments.

“There’s nothing else to do besides trying to get better every single day and focus on the rehab,” he said.

Between games, the Sox recalled righthanded reliever Luis Guerrero from Worcester and designated lefthander Sean Newcomb for assignment.

Guerrero, 24, appeared in three games earlier this season for the Sox, throwing four scoreless innings. He was erratic on Saturday, walking three and allowing two hits and a run in 1⅓ innings.

Newcomb, 31, had a 3.95 earned run average in 12 games, five of them starts. The Middleborough native made the team out of spring training and pitched well, striking out 41 in 41 innings.

Newcomb pitched one inning in the first game of Saturday’s doubleheader, allowing one run in the fifth inning of a 6-5, 10-inning victory.

The start of Game 1 was delayed for 26 minutes because of rain. There also was an unofficial seven-minute delay in the bottom of the first inning as the grounds crew attended to the field after a sudden downpour that sent the fans scrambling for cover. The sun was out by the time the Sox wrapped up the victory … The Red Sox-Rays game on Sept. 21 in Tampa was changed from 12:10 p.m. to 7:35 p.m. because of a conflict with the Jets-Buccaneers game, which starts at 1 p.m. … The Orioles made a roster move before Game 1. Outfielder Ramón Laureano (sprained left ankle) was placed on the injured list retroactive to Wednesday. Utility player Terrin Vavra was called up from Triple A Norfolk. Baltimore designated lefthander Cionel Pérez after the first game and called up righthander Yaramil Hiraldo.

Peter Abraham can be reached at [email protected]. Follow him @PeteAbe.