Iwakuma said he struggled with his mechanics during a 25-pitch bullpen session Friday, Josh Horton of MLB.com reports.

EDGE Analysis

Iwakuma's rehab from a shoulder injury suffered back in May just can't get off the ground. The Mariners were hoping to get him back in late August, but if Iwakuma can't get his bullpen sessions to move in the right direction very soon, that timeline will prove overly optimistic.