Martinez (elbow) is expected to begin a rehab assignment at Single-A Visalia next week, Steve Gilbert of MLB.com reports.
Martinez has been on the injured list all season while working his way back from Tommy John surgery. He's been cleared to face hitters for the past two weeks, and he's scheduled to pitch in a simulated game at the team's spring training complex this weekend before joining one of Arizona's minor-league affiliates. The 25-year-old righty will likely require an extended rehab assignment after spending more than a year on the shelf, but he could still make it back to the D-backs' bullpen before the end of August.