Penguins forward Jayson Megna collided with Mason with 3:33 remaining in the second period. Mason took off his helmet, blocker and glove while he kneeled in the crease during a timeout.
He played the remainder of the second period before being replaced by Ray Emery to start the third. Emery stopped 12 of 14 shots in a 4-3 overtime win.
Flyers coach Craig Berube said he was not sure of the severity of Mason's injury but expects him to be prepared to start Game 1 of the Stanley Cup Playoffs against the New York Rangers in the Eastern Conference First Round.
It's not always going to be pretty, especially against a great goalie [Lundqvist] like that. My goals are never how you draw them up. It's just a matter of grinding it out and trying to create havoc in front and good things happen.
— Capitals forward Jay Beagle on scoring in their Game 3 victory against the Rangers on Monday