PEORIA, Ariz. -- The Mariners suffered their first significant health setback of the spring Friday with word from general manager Jerry Dipoto that left-hander Drew Smyly has a flexor strain in his left elbow and will likely be sidelined for six to eight weeks.
Dipoto said fellow southpaw Ariel Miranda, who had been optioned to Triple-A Tacoma, will be recalled and will slide into Smyly's spot as the fourth starter.
Smyly was one of the team's biggest offseason acquisitions, and he was expected to open the season on Thursday behind Felix Hernandez, Hisashi Iwakuma and James Paxton in the rotation.
Instead, Miranda will start on Thursday at Houston, with veteran Yovani Gallardo remaning in the No. 5 spot and pitching in the opener of the Angels series in Anaheim on Friday.
"It's a key loss," Dipoto said. "I could sit here and lament the fact we 've lost Drew for a period of time, or I could take a positive outlook. We're days away from Opening Day, and it does nobody any good if we break [camp] with our heads down.
"Drew Smyly was and is important to our season. I anticipate he's going to contribute at some point, just not as soon as we expected. We're still very happy with the acquisition, loved what he looked like when he was here in Spring Training with us and believe he'll be an impact player for us at some point in the not-too-distant future."
Smyly looked extremely sharp early in camp and had a strong start for Team USA in the World Baseball Classic against Venezuela on March 15, but he was hit hard in a Minor League game on March 21, then gave up three home runs in his last Cactus League start in a four-inning stint against the Reds on Sunday.
After feeling discomfort in his arm following a throwing session on Tuesday, the 27-year-old was checked out by doctors and now is getting a second opinion.
Smyly's velocity was up in his lone outing for Team USA, when he struck out eight in 4 2/3 innings, but Dipoto doesn't know if that start created the injury issue.

"Drew was throwing great when he got to camp. He was throwing great when he left and threw in the WBC. We all watched it," Dipoto said. "Good, bad or indifferent, he just hasn't been quite the same since he got back. But injury can happen any place, so it's hard to point the finger back. I'd rather look forward and see how we create a solution rather than placing blame."
Smyly went 7-12 with a 4.88 ERA last year for the Rays while making a career-high 30 starts and throwing 175 1/3 innings, and Dipoto felt the lefty would be a perfect fit for the Mariners in fly-ball friendly Safeco Field with Seattle's much-improved outfield defense.
Miranda, a 28-year-old Cuban, was acquired from the Orioles for Wade Miley last July 31, and he went 5-2 with a 3.54 ERA in 11 outings (10 starts) in the final two months of 2016.
Miranda hasn't thrown in a game since March 24, but he says he's been told he'll pitch five innings in relief of Gallardo in Seattle's final Cactus League game Saturday against the Rockies.
"This is obviously what I wanted," Miranda said through translator Fernando Alcala. "I'm happy the club kept me in mind for when this situation arose. Now I just have to focus on geting the job done."