Realmuto (knee) exited Friday's game against the Marlins, Scott Lauber of The Philadelphia Inquirer reports.
Realmuto remained in the game briefly after fouling a ball off his left knee in the second inning. However, he was lifted in favor of Garrett Stubbs in the fourth frame. The severity of the issue is unclear, but the Phillies will likely be cautious with the 33-year-old catcher given their big lead in the NL East.