He should be able to get plenty of rest after a very successful return to the club on Wednesday night.
Wayne Simmonds gave Philadelphia a 2-0 lead less than four minutes after Giroux's quick strike, and Gagne scored his first goal of the season in the second period, one day after being reacquired by the Flyers from the Kings.
"It felt almost like I never left," said Gagne, who added an assist. "Just walking in the building before the game, knowing everyone. The nice welcome I got during the warm-up and after the first five minutes of the period. It's almost like coming back home.
"Everything started here."
Max Talbot stretched the advantage to 4-0 in the second, chasing goalie Braden Holtby to the bench just one day after his home shutout of Carolina. Talbot's slap shot hit the camera inside the net and quickly ricocheted out.
"Fourth goal was mine to have, but I have to put it behind me and move forward," Holtby said. "This is not what we wanted, obviously. But there are a lot of things we can learn from here."
Gagne, who will turn 33 this week, was acquired Tuesday from the defending champion Kings for a conditional draft pick. He appeared in his first game after being a healthy scratch for the past five games with the Kings.
Gagne hadn't scored since Nov. 17, 2011 -- a span of 28 games. He missed the final 46 games of last season because of injury.
He quickly gave a jolt to the Flyers.
"He's a guy that's well known here and well loved," Talbot said. "It brought a lot of energy and passion to the game. He was making plays out there, so he definitely gave us a big momentum."
A highlight video of Gagne's first stint with the Flyers was shown during the first period, officially welcoming the popular forward back to Philadelphia, where he spent his first 10 NHL seasons before being traded to Tampa Bay in 2010.
He seemed unaware of the video, at first, but then acknowledged the cheering crowd with a half-wave. Gagne received a louder ovation when he took a pass from Brayden Schenn feed and slammed a shot past Holtby for a 3-0 lead.
The Flyers have trailed 1-0 in 12 of their 20 games this season, but Giroux and Scott Hartnell combined to give them an early lead on Wednesday.
From his knees, Hartnell flipped the puck back to Giroux, who fired a rising shot past Holtby. It was the fourth time this season the Flyers scored in the first minute.
"It's great to have that lead right off the bat and keep it," Giroux said.
Hartnell, in his fifth game since returning from a broken left foot, added another assist on Simmonds' power-play goal. As Simmonds spun away from the net, he managed a backhanded flip that eluded Holtby.
Philipp Grubauer then made his NHL debut in relief of Holtby, and blanked the Flyers the rest of the way. Grubauer was called up on Tuesday from the Hershey Bears of the American Hockey League.
The Capitals (7-11-11) lost for the third time in eight games.
"It was a dream come true," Grubauer said. "I've dreamt about this since I started playing hockey, and it was amazing. I tried to step up and give those guys confidence and show the organization that I can do something, as well."
Tempers flared with 24.6 seconds left when Flyers' forward Harry Zolnierczyk delivered a shoulder-to-chest, east-to-west hit on center Mathieu Perreault just inside the Flyers blue line. Both coaches said it was a clean hit, though Zolnierczyk was given a major penalty for kneeing.
For the Capitals, it was another loss in their up-and-down season.
Washington failed to build on its win Tuesday night.
"It sure seems like that," Capitals defenseman Karl Alzner said. "Hopefully, that's not the way it continues to go, but that does seem to be the trend. We're still not where we want to be completely, but we're getting back there. It's not a good loss, but hopefully it doesn't set us back more than one game."
The Flyers (10-11-1) went 8-6-1 in February.
"We'd rather be 15-0, but we're not 0-15, either," Flyers coach Peter Laviolette said. "I think sometimes you get too focused on the ones that you lose, and lose sight of the big picture.
"Certainly, there are things this month that we could've done better, but it was the first month that really put us behind the 8-ball."
Flyers D Erik Gustafsson left the game shortly after blocking a shot in the second period and didn't return. The team said he has a lower-body injury. ... Gagne's goal was his 260th with the Flyers. ... Holtby made his eighth consecutive start for the Capitals. He was supposed to rest on Wednesday, but got the start because regular backup Michal Neuvirth was sick. ... Edmonton Oilers executives Kevin Lowe and Craig MacTavish watched the game from the press box.