Flyers coach Craig Berube believes Mason will be ready for Game 1 in New York, which is expected to be played Thursday. Berube said Mason was removed from the game for precautionary reasons.
"I think he'll be fine," Berube said.
Defenseman Mark Streit won it with 2 minutes, 50 seconds left in overtime, firing a backhander that deflected off defenseman Kris Letang's stick and off the stick of goalie Marc-Andre Fleury.
The Flyers won despite being outshot, 36-21, and twice giving up a lead in the waning minutes of regulation.
"Our team's got character. They come back, and they fight," Berube said.
"But we've got to play better. We've got to play better," he said. "We turned pucks over and didn't have any jump. I thought we were a step behind."
They won mostly because Mason made 21 saves - many of them acrobatic - and because Jake Voracek (two goals, assist) and Claude Giroux (goal, two assists) were dominating.
Giroux (three points) redirected Voracek's pass into the net with 1:15 left in regulation to give the Flyers a 3-2 lead. But Letang tied it at 3 with 36.8 seconds remaining, beating a slow-to-react Ray Emery after the puck caromed off the backboards out front.
With 3:33 left in the second period, Pittsburgh's Jayson Megna knocked Flyers defenseman Andrew MacDonald into Mason. The goalie's head and neck snapped back and he fell backward and hit the ice.
"He kind of just barreled over me," MacDonald said of Megna, who received a goalie-interference penalty.
Mason, who wasn't available to reporters afterward, remained in the game for the rest of the period, but Emery replaced him at the start of the third. Mason stopped 21 of 22 shots, enabling the Flyers to take a 2-1 lead into the third.
Pittsburgh tied it when James Neal's right-circle shot went through Emery's legs with 5:07 left in regulation.
The Flyers improved their regular-season record to 9-1-1 at the Consol Energy Center since it opened in 2010-11 - and 11-2-1 including the playoffs.
Sparked by their special teams, the Flyers won four of the five games against the Penguins this season. The Flyers were 6 for 15 on the power-play against Pittsburgh, while the Penguins were 1 for 21.
The Flyers, led by Sean Couturier, also snuffed a five-on-three Penguins power play Saturday that lasted 1:34.
Pittsburgh had a 12-0 shots advantage in the second period before the Flyers scored on their first shot of the period. Giroux's left-wing shot was deflected by Scott Hartnell, and Voracek knocked it into the net just before it was about to cross the goal line. That gave the Flyers a 2-1 lead with 5:22 left in the second.
There would be plenty of more theatrics and scuffles. There always is when these bitter rivals meet.