Mason declared himself out for Sunday's contest after practice Saturday. Though he skated for the second straight day, the 25-year-old Mason said he still is not feeling well enough to play. He will not be available to back up, either.
Backup netminder Ray Emery, who gave up four goals on 36 shots in the Flyers' 4-1 loss Thursday, will make his second consecutive start.
"For the most part, I felt pretty solid. Getting better every day, but I won't play tomorrow," Mason said.
Mason has not played since suffering an upper-body injury during the second period of the Flyers' 4-3 overtime win against the Pittsburgh Penguins last Saturday. Mason's exact injury is not clear, and he has declined to say whether he suffered a concussion.
Mason wouldn't say what is holding him out of the lineup currently, but indicated that he still has some improvement to make before he can return.
Mason spoke with both head coach Craig Berube and general manager Paul Holmgren at the end of the practice.
"Probably with the last 10 minutes of practice, what's been bothering me wasn't feeling very good," Mason said. "Just in talking with [Holmgren] and [Berube] there, we decided we needed a little more time before I get back in net."
Berube said previously that Mason's health remains the top priority.
"We talked it over as an organization and he's not ready," Berube said in his post-practice press briefing.
Mason said he is still hoping to be back at some point in the series, with Game 3 his next target. Following Sunday's matinee, the series shifts back to Philadelphia for Game 3 at Wells Fargo Center on Tuesday.
"I'm going to make [Game 3] my goal and get as much rest in as possible to make sure that when I get back in I'm 100% and ready to help the team rather than to be a liability out there," Mason said.
Mason was asked if he considered Saturday's development a setback.
"I think it's just part of the process," he said. "I think we're doing everything we can to make sure we're treating it in the proper way. As much as it is frustrating, I think everybody understands it's part of the process."
Emery, who has a 7-3-0 record against the Rangers, was strong in his first 2014 playoff appearance, holding the Rangers to just one goal through the first 48 minutes of play despite New York having a distinct territorial edge.
During the third period, he surrendered a pair of goals to the Rangers' power play with Philadelphia down a man for four minutes with rookie forward Jason Akeson in the box serving a double-minor hooking penalty. He later gave up another to Carl Hagelin, though Berube assessed his play positively.
"I thought he looked good. I thought he looked sharp," Berube said. "[Those] third-period goals were power-play goals that there was not much better that he could do on."
It is expected that depth goaltender Cal Heeter will back up Emery on Sunday.