Perez was diagnosed with a hamstring strain after leaving Sunday's game against the Rays, Anne Rogers of MLB.com reports.
Perez's injury was initially described as discomfort, but he's dealing with a strain. He'll undergo further testing to determine the severity of the issue, and the Royals expect to know more Monday. It's unclear whether the catcher will require a trip to the injured list, but Freddy Fermin and MJ Melendez could see additional time behind the dish if Perez is sidelined.