Maurer began last season in the Mariners' rotation and went 5-8 with a 6.30 ERA in 22 games. He'll replace Blake Beaven, who went on disabled list this week with a sore right shoulder. Beavan had been filling in for James Paxton, who is also on the DL.
All-Star right-hander Hisashi Iwakuma, who has been sidelined since the start of the season with a finger injury, threw 35 pitches in a simulated game Friday and said he felt no pain. He's expected to begin a rehabilitation assignment Tuesday with Tacoma.