Diaz (elbow) will begin a rehab assignment Monday for High-A Brandenton, Bill Brink of the Pittsburgh Post-Gazette reports.
If Diaz were healthy, there's a good chance he'd be with the Major League club at the moment, as both Francisco Cervelli (hand) and Chris Stewart (knee) are on the disabled list. Instead, the team had to claim Eric Fryer off waivers to ensure positional depth. That being said, the Pirates will likely keep a close eye on the 25-year-old's rehab assignment, as he could be an option for the team following the All-Star break. He has yet to play this season, however, so a somewhat lengthy rehab assignment could be on tap.