"It's my first time on the ice in a couple days, and it's a good step," Mason said. "I felt good."
Mason, who suffered two concussions earlier in his career, said he will "know exactly when I'm ready to go, physically, but it's also a management and doctor's decision as well."
The Flyers had a third-period meltdown (again) and suffered their ninth straight defeat at Madison Square Garden.
Friday was Mason's first practice since Tuesday. The Flyers will not say if he had a concussion. The goalie was injured Saturday in a goal-mouth crash in Pittsburgh after he made a save on Sidney Crosby.
Mason, who hasn't played in the playoffs since he was with Columbus in 2009, said it was "very frustrating" to sit out the opener.
"This is the time you've worked all season to get to, and to see the team go out there in a playoff atmosphere at Madison Square Garden, where the stakes are so high, it's something you don't want to be sitting out watching," said Mason, who praised the play of goalie Ray Emery. "It was difficult, especially since the result [wasn't what the team wanted]. I think everybody expects a much better game on Sunday. I don't think anybody was happy with the way the team played."
Goalie coach Jeff Reese was at Friday's practice, but was not permitted to comment on Mason's progress, per general manager Paul Holmgren's orders.
"His health is the most important thing," said coach Craig Berube, who was not at the practice, which had just three skaters, Mason, and goalie Cal Heeter as participants. "I've said that all along. I'll talk to him and see how he feels and talk to Jeff Reese and we'll go from there."
Mason will compete in a full practice with all his teammates Saturday and, if all goes well, he is expected to get the nod to start Sunday.
In three appearances against the Rangers this season, Mason went 2-1 with a 2.01 GAA and .937 save percentage.
"Mase has been solid for us all year," winger Scott Hartnell said. "Ray or Steve, we're going to be right there playing the same way in front of him."
They need to play better than they did Thursday or they will fall into a 2-0 hole - no matter who is in the nets.