Mats Sundin added a goal for the Maple Leafs, who are in danger of missing the playoffs for the first time since the 1997-98 season.
"We obviously understand that we're in a spot where we're probably going to have to win a lot of our games," Sundin said. "We're going to do everything we can to make it into the playoffs."
Aubin has added a surprising boost to Toronto since he was recalled from the AHL Marlies on March 14. He improved to 2-0 and had a 35-save effort in a win over New Jersey on March 26.
"It's all about confidence, and this team just played great and it makes me feel so comfortable when the players are playing that way," Aubin said. "Every game is big, especially for our team and me, too. I'm trying to get a job here for the future."
"It's the kind of game you look at at the end of the season and that may be two points we could have had in the standings," Flyers forward Simon Gagne said. "All the work we did the last few games was great, but to play the way we played tonight and not put the effort into at least getting the chance to get those two points is not the right way to do it."
Aubin stood up strong to a Flyers offense that snapped out of a funk in the third period. Philadelphia took only 14 shots in the first two periods before recording 16 in the third, including Umberger's 15th goal of the season with 4:55 left that made it 3-2.
The Flyers pulled goalie Antero Niittymaki after a Toronto penalty and played with a two-man skating advantage for the final 30 seconds, but failed to register a quality shot.
"We didn't check hard, we didn't play hard," Umberger said. "It finally caught up to us. We just squeaked by the first two periods."
The Flyers couldn't sneak out of the third with a win, and they lost for only the second time in seven games.
"We had the wrong attitude to start the game," Flyers coach Ken Hitchcock said.
The Maple Leafs surprised Niittymaki with two quick goals in the opening minutes of the third, ending a run of what had been sensational goaltending by the rookie. Niittymaki finished with 23 saves.
Only 18 seconds into the third, Ponikarovsky scored his 18th goal to make it 2-1. Almost before the crowd could stop booing, Steen followed with his 17th goal only 1:44 to give Toronto a 3-1 lead.
After the Flyers scored four goals in the first period in a win over Ottawa on Saturday, it looked like more of the same when Pitkanen fired a power-play slap shot from just past the blue line for his 12th goal only 3:58 in.
Sundin tied it for the Leafs with his 21st goal late in the first.
Aubin fended off some rapid shots late, and made the save of the game in the second period, snaring Michal Handzus' drive with a nifty glove save.
Niittymaki made his third start in four games. ... The Flyers' season-low shot total was 18 in a 4-3 win over Atlanta on Nov. 5. ... Flyers C Peter Forsberg had his 53rd assist. ... Sundin also added his 37th assist. ... The Maple Leafs return to Philadelphia on April 8.
Copyright by STATS LLC and The Associated Press
Arena: Wells Fargo Center Location: Philadelphia, Pennsylvania
Referees: Rob Shick Linesmen: Tim Nowak, Anthony Sericolo
Attendance: 19,651 (100.8% full)
Team Stat Comparison
Power Play Goals
Power Play Opportunities
Shots on Goal
Joni Pitkanen (12)
(Power Play) Assists: Sami Kapanen, Peter Forsberg