SEATTLE -- Matt Brash's hopes for a comeback in 2024 have officially ended, as the high-powered Mariners reliever underwent Tommy John surgery this week, general manager Justin Hollander shared on Friday.

Brash had the ulnar collateral ligament in his pitching elbow repaired and a brace installed on Wednesday by Dr. Keith Meister, the orthopedist that he’s worked with since first experiencing right elbow inflammation in early Spring Training.

The Mariners estimated Brash’s recovery in the range of “12 1/2 months for Major League activation,” Hollander said, targeting next June. The brace, which was installed around the repaired ligament, has typically allowed patients to begin physical therapy sooner, which is why the Mariners are hopeful Brash can return in 12 months. Brash’s surgery was not the same internal brace procedure that many notable pitchers have recently undergone, such as Atlanta's Spencer Strider in April.

“It could go faster than that; I would be excited if it did,” Hollander said. “I would hate to ever peg that as the most likely outcome, a sub-12-month rehab, but they feel really good about how the procedure went and his ability to rehab from it successfully."

Brash and Meister came to the decision shortly after Brash was shut down on April 27, just as he was preparing for a Minor League rehab assignment. At that time, Hollander said, Brash was experiencing issues bouncing back after each throwing session.

The MRI that Brash underwent with Meister in spring revealed inflammation, but he wasn’t experiencing pronounced pain, which is why he attempted a rehab route rather than surgery.

“He tested strong still,” Hollander said. “He felt good still. And so that is an injury that if you are asymptomatic, you can pitch through. Unfortunately, when he ramped up, as we discussed, it was not asymptomatic at that point. So whatever happened in Spring Training changed his sort of ability to pitch with the way the elbow was, the condition the elbow was in.

“Now that he felt pain, when [Meister] went in there, he saw an injury consistent with what the MRI showed in Spring Training. I can't say whether [the tear] is a little bigger or had changed spots or anything.”

Specifically, Hollander said, Brash experienced a small tear to the posterior area of the UCL.

“Every teammate loves Matt,” Hollander said. “What he did for us last year was unbelievable, how many times he came through for us.”

Brash led the Majors with 78 appearances last year and pitched in some of the Mariners’ highest-leverage spots, particularly after the club dealt closer Paul Sewald to Arizona at the Trade Deadline. He carried a 3.06 ERA and 132 ERA+ (league average is 100), with a 34.7% strikeout rate and 9.4% walk rate in 70 2/3 innings. His 2.1 wins above replacement, per FanGraphs, ranked fourth-highest among MLB relievers.

He’s also been at the center of some of the game’s best highlights among relievers over the past two years, with a wipeout slider and fastball that touched 100 mph.

Despite his absence -- and that of Gregory Santos, who has been sidelined since spring with a right latissimus dorsi strain -- the Mariners’ bullpen has stayed afloat, with a 2.39 ERA that ranks third-best in the Majors. Santos, who recently experienced a setback in his recovery, is expected to transition his rehab from Arizona to Seattle this weekend.

“We do think that pushes back his timeline obviously,” Hollander said. “Originally, we'd hoped at the end of May or early June. But now we're looking at July, just realistically where that is.”