Diaz (head) was placed on the minor-league disabled list Sunday.
The move, which is retroactive to May 18, comes after Diaz exited Wednesday's game at Double-A Jacksonville after getting hit in the helmet with a 90 mph fastball. Specifics regarding the injury remain unclear, as does a timetable for his return. Diaz was hitting just .194/.325/.336 through 37 games with the Jumbo Shrimp before suffering the injury.