"Not enough fight tonight," coach Craig Berube said. ". . . We didn't have our best players playing tonight."
Longtime Flyers nemesis Henrik Lundqvist made 30 saves, giving him his eighth 30-win season. Defensemen Dan Girardi and Ryan McDonagh cleared the net in front of Lundqvist throughout the game, and they also helped keep Flyers star Claude Giroux in check.
The loss dropped the Flyers three points behind the Rangers in the Metropolitan Division. The Flyers have two games in hand, but they also have a tougher schedule than New York.
"We're still fine here," winger Wayne Simmonds said. "We still control our own destiny."
Jake Voracek scored his 100th career goal to snap the shutout with 1 minute, 53 seconds left.
The Flyers, who have suffered back-to-back regulation losses for the first time since Jan. 23-25, are three points ahead of Columbus and Washington in the division race.
The Rangers, winners of five straight, locked up the victory when Dominic Moore's deflection tricked through the legs of Mason with 12:21 left, putting New York ahead, 3-0.
New York had taken a 2-0 lead as McDonagh scored from the right circle, beating Mason with a high shot to the short side with 14:26 remaining in the second.
The goal, McDonagh's 14th, was scored after Andrew MacDonald replaced Kimmo Timonen, who blocked Brian Boyle's shot with his left foot and left the ice a few shifts earlier. Timonen returned later in the period.
The Rangers, who played without injured winger Chris Kreider, dominated the second period, keeping the puck in the Flyers' end and frustrating the top unit of Scott Hartnell, Giroux, and Voracek. That line combined for just three shots in the first two periods, none by Giroux.
Giroux said the Flyers looked tired. He hinted they may have been drained by their recent five-game winning streak, mostly against NHL heavyweights.
"Let's be honest. We played a lot of good teams lately and we had some big wins and worked hard," he said. "There's not a lot of [off] nights here, and coming up we have to make sure we get some rest."
Unlike their previous visit to New York, the Flyers controlled the first period, but despite a 15-6 shots advantage, they faced a 1-0 deficit after the opening 20 minutes.
Mason went behind the net and sent a pass along the boards to Timonen, but the puck hopped over the defenseman's stick to Boyle. Boyle fed Derek Dorsett in front, and he put a backhander past Mason.
The Flyers have 10 games left, and seven are against teams in the playoff hunt, including Friday's matchup against James van Riemsdyk and visiting Toronto.
The Rangers have a much easier schedule: Only two of their remaining eight games are against teams in playoff spots.