In his first NHL game on January 8, 1985, he scored two goals including the game-winner in a 5–3 victory over the Vancouver Canucks in Philadelphia.
In the playoffs that year he led all rookies with 13 points, and helped the Flyers reach the 1985 Stanley Cup Finals.
Bergen said he lost his love for the game because of Keenan and the Flyers, and announced his retirement in September 1985 to pursue a professional golfing career.
There was speculation that Bergen was holding out because he was trying to get away from Keenan, to which general manager Bobby Clarke responded, "Who am I gonna trade him for, Lee Trevino?"
Bergen was traded by the Flyers (with Ed Hospodar) to the Minnesota North Stars for Dave Richter and Bo Berglund on November 29, 1985.
Bergen now owns a tackle business in Campbell River, British Columbia called Dymara Industries.