Diaz (elbow) will undergo surgery on his right elbow this week, although the Pirates are confident that there is no UCL damage, Stephen J. Nesbitt of the Pittsburgh Post-Gazette reports.
Fortunately for Diaz, it seems that he'll be able to avoid Tommy John surgery, but elbow surgery still will keep him on the shelf for some time. This really hurts the Pirates catching depth for this season, as they are fairly thin beyond Francisco Cervelli and Chris Stewart. A timetable for Diaz's return is currently unknown, but more details should surface after the surgery is complete.