Diaz was recalled from Triple-A Indianapolis on Saturday, the Pittsburgh Post-Gazette's Stephen Nesbitt reports.
Eric Fryer was placed on the paternity list, so Diaz was summoned to provide short-term catching depth behind Francisco Cervelli. Diaz was reinstated from the 60-day DL a couple days ago and optioned to Triple-A after missing the first three-plus months of the season with an elbow injury. He figures to be sent back to Triple-A once Fryer rejoins the Pirates.