Philadelphia's loss, coupled with Pittsburgh's win over New Jersey, shaved the Flyers' divisional lead over the Pens to just one point with two games remaining.
Mike Richards recorded a pair of power-play goals and Sergei Bobrovsky stopped 21 shots for the Flyers, who also dropped out of the Eastern Conference top spot with the setback and Washington's win over Toronto.
The Capitals, with 105 points, lead the Flyers by two points for the East's first seed.
Astronomers offer more expansive view of universe
McPhee, Cokas 'working on their marriage' after affair