Rios was traded from the Rays to the Mariners on Friday in exchange for cash considerations.
Rios was unable to break camp with the Rays to begin the year, but he's been dominant with Triple-A Durham. In 12 relief appearances, he's posted a 0.66 ERA and 0.76 WHIP in 13.2 innings. The right-hander has appeared in the majors in each of the last four seasons, but he'll likely report to Triple-A Tacoma going forward.