Brian Boucher, making his first start in the series, made 35 saves to help the Flyers take a two-games-to-one lead in the best-of-seven Eastern Conference quarterfinals - and regain the home-ice advantage in this physical, no-love-lost series.
Kimmo Timonen, who contributed mightily to a key five-on-three penalty kill in the third period, iced the win with an empty-net goal with 17.8 seconds left.
Zherdev has had a different outlook since no one claimed him off waivers.
"Since that time, what's been most impressive to me is his attitude," coach Peter Laviolette said. "He's worked really hard, and he's committed just like everybody else. He got an opportunity tonight and scored a big goal for us.
"There's always two different roads you can go down at that point," Laviolette said, referring to the waiver situation. "You can go south and maybe never get a player back, or you can do what you have to do, and he's worked really hard with the coaches and very hard with [trainer] Jimmy McCrossin to keep himself in shape."
Game 4 is Wednesday in Buffalo.
With 13 minutes, 1 second left, Buffalo had a five-on-three power play for 1:15, but the Flyers killed it off skillfully, allowing just one shot in that span. Defensemen Timonen (plus-three) and Braydon Coburn (plus-three), and center Mike Richards did the bulk of the work on the two-man disadvantage.
"That," said Boucher, whose team got a breather when he needed a mask repair during the penalty kill, "was the pivotal part of the game."
In the franchise's history, the Flyers are 18-3 when they have a 2-1 lead in a series.
Ex-Sabre Danny Briere, a certified Buffalo killer, gave the Flyers a 2-1 lead by converting a Scott Hartnell pass with 17:36 left in the second period.
Hartnell pressured defenseman Chris Butler into overskating the puck behind the net. Hartnell then found Briere, who has five goals and four assists in seven games in Buffalo since he became a Flyer.