SEATTLE -- Rafael Montero's time in the Mariners bullpen has come to an end.

The club designated the right-hander for assignment on Friday to clear a 26-man roster spot for Casey Sadler, who was activated from the 60-day injured list after a three-month recovery from right shoulder inflammation.

The transaction puts a disappointing, but perhaps necessary, bow on Montero’s stint with Seattle, one that began on Dec. 15 when he was acquired from Texas to be the club’s closer but featured one rocky outing after another that slowly lost his grip on leverage moments.

Montero’s final outing on Thursday was a microcosm of his season. Staked with a one-run deficit in the eighth inning against the bottom of Oakland's lineup, Montero worked himself into a bases-loaded jam and surrendered two runs to put the 4-1 contest out of reach.

“Rafi, acquiring him in the offseason coming in, I have to say, without a doubt all my years in the big leagues, a tremendous person and the most unlucky pitcher I've ever been around when you look at the numbers and how it all worked out,” Mariners manager Scott Servais said. “But I've often said this is a game, it's a do-good league. You do good, you stay, and it's about results. So, unfortunately, we had to make a move there.”

The Mariners now have seven days to trade Montero, place him on irrevocable waivers or release him. Given that Montero possesses strong stuff, it’s possible other clubs may be interested in him, but his 7.27 ERA and 56 ERA+ (league average is 100) in 43 1/3 innings will make it incredibly hard to trade him, especially given that many top-end relievers are available ahead of the July 30 Trade Deadline.

If Montero is claimed, the acquiring club would have to obtain his blessing in order to send him to the Minors due to his four-plus years of Major League service time. And that itself almost certainly eliminates the possibility of Montero accepting an outright assignment to Triple-A Tacoma. The likeliest outcome is that Montero will be released.

“I'm pretty confident that he'll get a shot somewhere else,” Servais said. “He still has good stuff. And sometimes, just change of scenery, put a different uniform on, and you get a fresh start, and you take off and go from there.”

Montero was the headliner in general manager Jerry Dipoto’s offseason overhaul to the bullpen, which also included signing Keynan Middleton to a one-year Major League contract and re-signing Kendall Graveman to a big league deal. But other arms have emerged as their best weapons as the season has pressed on, notably Paul Sewald, Drew Steckenrider and JT Chargois.

A bullpen’s conduciveness to fluidity could certainly position Sadler to carve out a leverage role for himself. Before he was placed on the IL on May 2, Sadler had a 1.64 ERA and had held 46 opposing hitters to a .205/.304/.282 (.586 OPS) clip in 11 outings.

And considering that Seattle’s ‘pen could look even more different after next Friday’s Deadline -- with Graveman and Steckenrider as possible trade chips -- Sadler could indeed have a far more prominent role, health-pending, as the season moves on.

“He’s been really good,” Servais said. ”He was good when we picked him up last year. He was off to a good start to season. He had a little bit of a shoulder issue. He’s worked through that and he looks good.”