Colin Campbell says linesman Tony Sericolo made a "mistake" by not calling offside on Danny Briere's first goal in Game 1 of the Penguins- Flyers series Wednesday night.

The NHL senior executive vice president of hockey operations told The Canadian Press that there was "no other way to explain it but a missed call."

"We're as upset as Pittsburgh, almost. It's a mistake," Campbell said.

Briere, with two goals in the game, scored the first in the second period when Brayden Schenn's lead pass hit him in stride. Replays showed, however, that he was offside.

The Flyers overcame a 3-0 deficit in the first period to stun the Penguins, 4-3, in overtime.

Game 2 of the best-of-seven series is Friday night in Pittsburgh.