Starting pitcher James Paxton limps off the field with the help of Manager Alex Cora, left, and a trainer in the first inning of the Red Sox’s 10-2 loss to the Astros on Sunday at Fenway Park in Boston. Michael Dwyer/Associated Press

James Paxton has been back with the Red Sox for less than a month, but he was high on the list of players they couldn’t afford to lose.

On Tuesday, Red Sox Manager Alex Cora said the veteran left-hander’s season could be over. Paxton was diagnosed with a partial tear of his right calf.

“We’ll see where we’re at in a few weeks, but just stay the course, you know, get the rehab going, and hopefully he can contribute,” Cora said. “But that looks like a long shot.”

Paxton, 35, exited his Sunday start after 2/3 innings and just five pitches to three total batters. Even with help from the coaching staff and trainers, he could barely walk off the mound. In the subsequent days, he’s hobbled around the clubhouse on crutches, a concerning sight before the Red Sox even had the official diagnosis.

“I think right away, he had a pretty good idea what was going on,” Cora said.

The Red Sox first signed Paxton to a one-year deal with a two-year club option or, if declined by the team, a one-year player option before the 2022 season, as he recovered from Tommy John. When he took the mound for his first rehab outing that August, he suffered a Grade 2 lat tear, ending his season.

Paxton made his Red Sox debut on May 12, 2023, and pitched well for the club in the first half, earning American League Pitcher of the Month honors in June. He struggled in the second half, however, and right-knee inflammation officially ended his season in early September.

He signed a one-year deal with the Dodgers in the offseason and made 18 starts for them. His last start with Los Angeles was against the Red Sox. He was designated for assignment the next day and traded to Boston.

The plan is to slot Cooper Criswell back into the rotation when he comes off the COVID-related injured list, which could be as early as Friday. But without Paxton, the Red Sox rotation is back to being a righties-only operation. And with the trade deadline in the rearview mirror, there’s no real way to fix that.

DODGERS: Los Angeles right-hander River Ryan will require Tommy John surgery for the elbow injury that he suffered Saturday while making his fourth major league start.

The Dodgers announced that Ryan would have the ligament-replacement operation next week. The team had already said Ryan would miss the rest of this season. The surgery will likely force him to miss most if not all of 2025, as well.

The 25-year-old Ryan went 1-0 with a 1.33 ERA in four starts for Los Angeles this season. He was 0-0 with a 2.22 ERA in eight minor league starts.

After the Dodgers’ 4-1 victory at Pittsburgh on Saturday, Ryan said he started to feel tightness in his forearm in the third inning. He was removed from the game in the fifth.

YANKEES: Third baseman Jazz Chisholm Jr. appears headed to the injured list with a left elbow injury, Manager Aaron Boone said.

The 26-year-old Chisholm has a probable ulnar collateral ligament injury and Boone said he will “likely” end up on the IL. He said more physicians are evaluating the elbow and that the club should have enough information to make a decision by Wednesday.

Chisholm was hurt on a headfirst dive scoring in the fifth. He left during the seventh inning of Monday’s 12-2 loss to the White Sox but downplayed the injury after the game.

RAYS: Tampa Bay recalled infielder Junior Caminero, the No. 2-rated prospect in Major League Baseball, from Triple-A Durham on Tuesday.

Caminero hit .276 with 13 homers and 34 RBI in 53 games for Durham. The 21-year-old has been sidelined twice this season with quadriceps injuries.

Caminero played in seven games with the Rays last year, hitting .235 with one homer and seven RBI.

Curtis Mead was optioned to Durham. The infielder was batting .238 with one homer and seven RBI.

METS: Rookie pitcher Christian Scott has started a throwing program with the hope of rejoining the New York lineup this season after being sidelined due to a sprained ligament in his pitching elbow.

The Mets’ top pitching prospect threw 35 times at a distance of 75 feet, after throwing approximately 25 times from 60 feet on Sunday.

Scott, who is 0-3 with a 4.56 ERA in nine major league starts since making his debut May 4 with an impressive performance at Tampa Bay, was put on the injured list on July 22 with a sprain of the ulnar collateral ligament in his right elbow. The 25-year-old is hoping to get back in action this season.