OAKLAND -- While the Mariners bullpen has been a pleasant surprise so far this season, that group took another hit on Tuesday as hard-throwing rookie Tony Zych became the fifth reliever to go on the disabled list since the start of Spring Training as a result of soreness in his right shoulder.
Zych flew home to Seattle on Tuesday to have Mariners physicians check out what was tentatively diagnosed as tendinitis in his rotator cuff. The Mariners called up right-hander Steve Johnson from Triple-A Tacoma.
Veteran setup man Joaquin Benoit went on the 15-day disabled list with shoulder inflammation last week and left-hander Charlie Furbush and right-handers Evan Scribner and Ryan Cook have been sidelined since early in Spring Training.
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Manager Scott Servais said he had no time estimate on Zych's absence as the club awaited his evaluation in Seattle.
"He's had some nagging soreness in his shoulder for the last week or 10 days," Servais said prior to Tuesday night's game against the A's. "That's why he hasn't been in there consistently. I've tried to give him some downtime. Although he threw the ball outstanding on Sunday, he came in yesterday and was real sore. So we thought it was best to get him checked out."
Zych, 25, has a 3.00 ERA and 19 strikeouts and eight walks in 12 innings across 10 outings this season. He struck out the side in a perfect frame Sunday against the Royals, his only appearance in the past six days.
Zych opened eyes as a September callup last year and has been a key part of a Mariners bullpen that posted a 2.41 ERA in Seattle's first 25 games this season.
Now Johnson joined that mix after going 1-0 with a 2.25 ERA in 16 innings over seven relief appearances with Tacoma. The 28-year-old pitched parts of the past three seasons with the Orioles and signed as a Minor League free agent with Seattle on March 16 after being released by the Rangers late in spring.
"It's obviously awesome to be called up," Johnson said before his Mariners debut in Tuesday's 8-2 win, in which he allowed a solo home run in one inning of work in the ninth. "It's my first time with another organization. I just worked hard in the Minors and thankfully got the call. I'm here to help."

Johnson appeared in six games for the Orioles last season, posting a 10.13 ERA in 5 1/3 innings. He's 5-1 with a 4.25 ERA in 27 Major League games with Baltimore in his career, including five starts in 2012-13.
With Zych out, the Mariners don't have any big power arms in their 'pen, but Servais said the group can still get things done.
"We still have strikeout guys, they just don't all throw 95 or 96 like Tony does," he said.
Servais said Nick Vincent will be an increasing late-inning presence. Vincent has a 1.74 ERA with 13 strikeouts in 10 1/3 innings. Joel Peralta and Vidal Nuno will continue working in the right- and left-handed setup roles and Servais said southpaw Mike Montgomery might appear in more high-leverage situations now.
If Johnson needs any advice on his own role, he need only call his dad, former Major League pitcher Dave Johnson, who played with the Pirates, Orioles and Tigers from 1987-93.
"He's been a huge influence," Johnson said. "He's taught me everything. It's nice to have someone who has been through the exact same thing as you, going through the grind of the Minors and then getting that call up and sent back down and all that. Mentally, it's nice when you're talking to someone to have it be your dad to know exactly what you're going through and having him there. He's been great for me."