OAKLAND — The Rays have a key vacancy to fill at the back end of their bullpen, as closer Pete Fairbanks was placed on the 15-day injured list with a right lat strain ahead of Monday’s 3-0 loss to the A’s at the Coliseum.

Fairbanks sustained the injury during Sunday’s 12-inning walk-off victory that sealed a sweep of the D-backs. Two batters after allowing a game-tying three-run homer in the ninth, Fairbanks threw a pitch, then immediately signaled to Tampa Bay’s dugout that he needed to be checked on. After a quick meeting with manager Kevin Cash and an athletic trainer, Fairbanks exited the game.

An MRI on Monday confirmed that the injury was a lat strain. Cash said Fairbanks will likely be shut down from throwing for 2-4 weeks, but the Rays should have a clearer idea of his timeline around when their next homestand begins on Aug. 30.

With six weeks remaining in the regular season, that could put a return this year in question.

“We’ll have a better understanding probably right about the time we get back from the road trip, seeing how he’s feeling,” Cash said. “But we’ll be cautious with everything and then see if we can build him back up. But we’ve got to let it heal for a little bit. Not much you can do other than rest it and probably some treatment.”

Fairbanks had previously dealt with a lat strain in 2022, missing roughly half the season after sustaining the injury during Spring Training.

Before the three-game set against the D-backs, in which he allowed five runs in 1 2/3 innings across two appearances, Fairbanks had been on a roll. He hadn’t allowed a run in nine outings before the weekend series.

Fairbanks was one of the anchors of a Rays bullpen whose 2.28 ERA since the All-Star break ranked second in the Majors entering Monday, even after Tampa Bay dealt setup man Jason Adam to the Padres ahead of the July 30 Trade Deadline.

Cash indicated that he might not name a temporary closer while Fairbanks is sidelined, at least not for now. The Rays’ skipper pointed to the rise of Edwin Uceta and Manuel Rodríguez, who have both emerged as reliable arms who can be trusted in high-leverage situations, as a positive while the team figures out how to handle the ninth inning.

But the different-look back end of the ‘pen was not put to the test on Monday, as the Rays never held a lead en route to being shut out for the sixth time this season.

Tampa Bay fell behind early after JJ Bleday took starter Taj Bradley deep for a two-run shot in the first inning. Bradley ended up bouncing back nicely from a string of three tough outings — across which he allowed 15 earned runs in 14 innings — by recording his first quality start since July 25 against the Blue Jays.

The bullpen followed Bradley with two scoreless frames, but the Rays’ offense scuffled to the tune of a season-low-tying two hits.

“Today’s a better day than what the past three outings have been, so I’m happy about that,” said Bradley, whose only other run allowed in his six innings on the mound came by way of a sacrifice fly from former travel ball teammate Lawrence Butler. “Just a hard-fought game. … It was good that I came out with a quality start like that, and just keep looking forward to something better.”

With Tampa Bay trailing in the late innings — but the game still within reach — Cash turned to left-hander Richard Lovelady in the seventh and righty Joel Kuhnel, who was the corresponding move for Fairbanks’ IL placement, in the eighth.

In addition to Uceta and Rodríguez, Garrett Cleavinger, Kevin Kelly and Colin Poche could all feasibly be options to close out games. All five should be relatively fresh should the Rays find themselves in a save situation on Tuesday.

It’s no easy feat to replace an arm like Fairbanks, but a bullpen that has been as dominant as the Rays’ in the second half should find a way to share the load.

“It’s a big absence, there’s no doubt,” Cash said. “[Fairbanks is] probably not a guy that we’re going to be able to replace with one guy. We’re going to need a pretty collective group effort.”