Robles (pectoral) will begin a rehab assignment at Triple-A Tacoma on Sunday, Adam Jude of The Seattle Times reports.
A strained right pectoral sent Robles to the injured list April 8, and he's now been cleared to return to a game environment after a few weeks of ramping up baseball activity. It's unclear exactly how long the Mariners plan to keep the 28-year-old in the minors, though he isn't expected to require a lengthy rehab assignment.