CLEVELAND -- When left-handed reliever Josh Walker rejoined the Mets last week in Philadelphia, no one was gladder to see him than Jake Diekman, who went out of his way to greet his younger teammate in the clubhouse. For two weeks, Diekman had been the lone lefty in New York’s bullpen, pitching on a roughly every-other-day basis as a result. The idea of some help seemed nice.

For the Mets, it’s a problem that won’t grow any easier in the months to come. The team’s top left-handed reliever, Brooks Raley, has opted to undergo an elbow operation that will likely end his season, manager Carlos Mendoza said Tuesday. As a result, a team already navigating its share of trouble must face the rest of the year without a potent bullpen weapon.

Mendoza said it’s not yet clear if Raley will undergo traditional Tommy John surgery or an internal brace procedure, which tends to carry a shorter recovery timeline. Either way, Raley is almost certainly done for the year.

“Guys are going to have to step up,” Mendoza said.

Without Raley in the Mets’ bullpen Tuesday at Progressive Field, Diekman allowed a two-run, sixth-inning homer to right-handed pinch-hitter David Fry, which wound up being the difference in a 7-6 loss to the Guardians. Mendoza complimented Diekman’s execution of the pitch, a 94-mph fastball near the up-and-away corner of the strike zone. But Fry’s ability to damage it overshadowed any moral victories, just as starting pitcher Adrian Houser’s mechanical improvements meant little within the context of the six earned runs he allowed.

In the dugout following his removal, Diekman picked up a cooler and smashed it to the floor -- a scene similar to one last week at Citi Field, when Diekman fired his glove at the wall and kicked the ground violently after a notably poor outing.

“Some days, you’re the bug,” Diekman said. “Some days, you’re the windshield.”

Diekman’s solid history over a 13-year career suggests he’ll be just fine in the long-term, as does his elite strikeout rate this season. But he can’t do it alone. Without Raley in the mix, Mendoza referenced Walker and Danny Young as two other options who must step up. A third left-handed reliever, prospect Nate Lavender, recently underwent an elbow brace procedure of his own and won’t return until 2025.

“We’re going to have to piece it together not only with lefties, but with some of the righties that are capable of getting lefties out too,” Mendoza said. “So it’s a big loss for us, but it will be an opportunity for somebody else, and guys will step up.”

Raley, whom the Mets acquired from the Rays prior to last season, was one of the league’s finest lefty relievers that summer (despite reverse platoon splits that were likely more a sample-size quirk than anything). For his career, Raley has held left-handed hitters to a .191/.263/.293 slash line, with much of his success coming since 2022.

But in mid-April, Raley began having trouble recovering from outings. Initial tests revealed only inflammation, but when Raley continued feeling discomfort following a cortisone shot, he sought a second opinion from orthopedic surgeon Dr. Keith Meister. That showed ligament damage. Raley recently traveled to Texas to meet Meister in person and, after exhausting all reasonable options, decided to undergo surgery.

“It sucks for him -- like, it sucks,” Diekman said. “I know he tried to do everything he could. I just don’t think it ever got better.”

Before Tuesday’s game, Raley reached out to several Mets, including Diekman, to deliver the news. Because the 35-year-old Raley has a clause in his contract, he can become a free agent in November despite having fewer than six years of service time. As such, he may have already thrown his final pitch with the organization.

“At least he has some sort of certainty,” Diekman said. “But that [stuff] happens all the time. We have seven, eight guys down there that can pitch whenever. I don’t think we have any guys with egos. So when the phone rings, if it’s the fifth, if it’s the eighth, if it’s whenever, it’s your job to throw a scoreless inning.”