Perez left Friday's game against the Royals after throwing to second base in an attempt to catch Kyle Isbel stealing, Evan Webeck of The San Jose Mercury News reports.
Perez immediately headed for the dugout after making the throw, seemingly in quite a bit of pain. The Giants will take a look at him and should provide an update relatively soon. If he's forced to remain out for an extended period of time, Blake Sabol would become the only active catcher on San Francisco's roster. Joey Bart (back) is set to begin a rehab assignment soon, but depending on the severity of Perez's injury, his return could be accelerated.