Giroux started the play that led to Sean Couturier's tiebreaking goal at 5:57 of the third period, making a diagonal pass through the offensive zone to Simmonds. He centered it to Couturier, who scored after Jimmy Howard saved his initial attempt.
"This year right from Day One he's been at a real high level," Flyers coach Dave Hakstol said of Giroux. "You look at his energy level, his compete level. The compete level has never changed in my opinion. But the energy level and his ability to get where he wants to go and be in on the fight seems to be and has been at a high level all year."
Mike Green had a goal and an assist for the Red Wings (13-14-7), who won 6-3 at the New York Islanders on Tuesday. Gustav Nyquist and Martin Frk scored, and Howard made 27 saves.
"I thought we did have guys play lots of minutes the past two nights," Detroit coach Jeff Blashill said. "It seemed like we didn't have as much push as we needed to have."
Hagg tied it 3-3 at 13:40 of the second period with his first NHL goal, a slap shot from the left point that went between Couturier's skates. Giroux got an assist with a backhand pass off the right wall.
Green's power-play goal at 5:50 of the second period gave the Red Wings a 2-1 lead. The Flyers tied it 2-2 on Simmonds' power-play goal on a set-up by Voracek at 10:48, and the Red Wings made it 3-2 41 seconds later on a goal by Nyquist.