SEATTLE -- Austin Adams, who has been one of the Mariners’ brightest additions this season, was placed on the 10-day injured list on Saturday along with fellow right-handed reliever Dan Altavilla as Seattle’s bullpen continued its revolving door.

Rookie right-handers Parker Markel and David McKay were recalled from Triple-A Tacoma to fill their spots in time for Saturday night’s game against the A’s at T-Mobile Park.

Adams has a Grade 1 (the least severe) strain in the lat muscle behind his right shoulder and will likely miss at least a few weeks, while Altavilla is dealing with a right forearm strain and got an MRI on Saturday afternoon to learn more.

“It’s disappointing,” said manager Scott Servais, whose team now has seven relievers on the injured list. “They were both throwing really, really well and we were starting to get a little stability in our bullpen. But [stuff] happens and we’ve had a lot of [stuff] happen this year, so we’ll keep moving forward.”

The 28-year-old Adams is 1-1 with nine holds and a 3.47 ERA in 21 appearances, including two starts as an opener, since being acquired from the Nationals on May 4. Adams has racked up 41 strikeouts with 11 walks in 23 1/3 innings.

Adams’ ERA with the Mariners jumped from 2.38 in his last outing when he gave up three runs on two hits and a walk in two-thirds of an inning in a 5-2 loss to the Cardinals on Wednesday.

Adams said he’d had some typical tightness in his shoulder recently, but didn’t think much of it. But when the issue didn’t get any better, the training staff suggested he get an MRI and the results showed the strained muscle.

“It is interesting to go back and look at [his last outing] and see where all my misses were, arm-side high,” Adams said. “I wasn’t able to get to my glove side. So that’s kind of understandable now.

“Obviously I’m pretty disappointed about it. I was feeling really good, and building a lot of confidence and pitching well for the team. It just sucks that this happened kind of out of nowhere.”

Adams is a prime example of what the Mariners have been trying to do this season, in unearthing relievers with upside who hadn’t been getting opportunities with other clubs for various reasons. The team has shuffled through 35 pitchers this year, including 23 relievers, in its first 93 games.

Adams is one who grabbed hold of the opportunity and appears part of the club's future plans.

“He’s been awesome,” Servais said. “A heckuva pickup. He’s really taken and run with a few things we’ve thrown at him and grown into a spot, you trust him in leverage situations and he’s been striking a lot of really good hitters out. He’ll be missed here. But it gives another opportunity to somebody else to step up.”

Altavilla, 26, had been throwing well in his past few outings while regaining his velocity, hitting 98-99 mph with his fastball. But after three straight scoreless outings with just one hit, four strikeouts and no walks, he allowed two runs on a hit and two walks in Friday’s 5-2 loss to the A’s in his first back-to-back appearances since being recalled on June 21.

Altavilla missed nearly three months last year with a flexor mass issue in his elbow. Servais said his current injury appears to be more of an ulnar collateral ligament problem, but the club will wait to find out more from the MRI.

Markel and McKay both were with the Mariners earlier this season. Markel gave up six earned runs over 3 2/3 innings in four appearances between May 12-20. Since returning to Tacoma, he’s posted a 3.94 ERA with four saves in 16 innings over 12 games.

Signed out of independent league ball this spring, the 28-year-old earned a Triple-A All-Star selection and is 2-0 with a 2.81 ERA in 20 overall outings for Tacoma, with 42 strikeouts and 20 walks in 25 2/3 innings.

McKay, 24, will be making his third stint with Seattle this season, though he didn’t appear in a game in his first callup. He allowed one earned run over five innings in five appearances in his second opportunity from May 19-31 and has gone 3-0 with a 3.76 ERA in 38 1/3 innings over 24 relief appearances for Tacoma.

Strickland progressing in his rehab

Right-handed reliever Hunter Strickland threw a 20-pitch bullpen session on Saturday and said it “felt awesome,” as he continues working back from a Grade 2 right lat strain that has sidelined him since March 28.

Strickland, who opened the season as Seattle’s closer, will take a few days off for the All-Star break and then throw one more bullpen session. He'll then advance to live batting practice and head out on a Minor League rehab stint if all goes to plan.

“Mentally, physically, everything, I feel like I’m ready to go,” he said. “It’s a good stepping stone to go into the break, and then we can just build off it when we get back."

Strickland is one of the many relievers hoping to return from the IL at some point in the second half, along with Brandon Brennan (right shoulder), Connor Sadzeck (right elbow), Sam Tuivailala (right Achilles), Chasen Bradford (right elbow) and now Adams and Altavilla.