Mason appeared to suffer a non-contact injury, possibly to his back. NJ.com's Randy Miller reported that there was "no one around him and he fell down." Mason was "slumped over" as he was helped off the ice, Miller added.
Mason, 26, has started 21 of Philadelphia's 31 games this season. He has a 2.49 goals-against average and a .921 save percentage.
Veteran Ray Emery is the team's backup goaltender. Emery has a 3.05 GAA and an .899 save percentage.
The Flyers' next game is Saturday in Toronto against the Maple Leafs.
- Dan Gartland