Iwakuma will be out 4-to-6 weeks with right shoulder inflammation, MLB.com's Greg Johns reports.

EDGE Analysis

He underwent an MRI earlier in the week, and the inflammation was deemed serious enough that he can be ruled out until at least mid June. Four of the Mariners' top five starters are on the disabled list, so stand-ins Chase De Jong, Christian Bergman, Dillon Overton and Ariel Miranda will likely remain in the rotation for now.