Thomas Vanek, Dominic Moore, Derek Roy, and Chris Butler scored for Buffalo, which is trying to climb back into playoff contention but has only one win in its last six games. Patrick Lalime stopped 25 shots.
Philadelphia remained tied with Pittsburgh for fourth place in the Eastern Conference. Both teams have 86 points.
Briere, the former Buffalo captain who last had a two-goal game on Oct. 18 at San Jose, tied it at 3 with 2:40 to go in the second period, slapping in a rebound from about 12 feet out. He then scored the go-ahead goal with 35 seconds remaining, firing in a slap shot from the slot.
Knuble added an insurance goal 4:31 into the third period, batting in a rebound from in front. The goal was only granted after a lengthy video review proved to be inconclusive, thus upholding the ruling of the on-ice officials.
Carter finished off a 2-on-1 with 2 minutes to go, and Butler scored a last-ditch goal with 1.2 seconds remaining.
In the first period, Richards missed on a penalty shot with 2:14 remaining, ringing his wrist shot off a goalpost. He made up for it 42 seconds later, opening the scoring on a low wrist shot which got between two defensemen and past Lalime.
In a back-and-forth second period, each team scored three times. Buffalo grabbed a 2-1 lead on goals by Vanek and Moore in the first 6:22, but Gagne tied it at 2-2 with a power-play goal at 10:14. Roy again put the Sabres up with 5:54 to before Briere scored twice to put Philadelphia back on top.
The Flyers swept the four-game season series against Buffalo, outscoring the Sabres 19-8. It was Philadelphia's first season sweep of Buffalo since winning all four meetings in 2000-01. Notes: Philadelphia will conclude its current four-game road swing Sunday in Pittsburgh. ... Richards has three goals and eight assists in his last nine games. Gagne has four goals and seven assists in his last nine. ... Moore's goal was his first point as a Sabre. It came in his seventh game with the team after being acquired from Toronto at the trade deadline.
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