The 25-year-old, who will become a restricted free agent in July, on Friday informed the Flyers he has signed a contract to play with Avangard Omsk of the Kontinental Hockey League. The Russian club announced the signing on its official Twitter account.
"I spoke with Erik [on Friday] and he informed me that he does in fact have a deal in place to play overseas," Flyers general manager Ron Hextall said. "Although we are disappointed in his decision, we wish him all the best."
Gustafsson had 10 points and a plus-7 rating in 31 regular-season games averaging 17:31 of ice time per game. He had one goal in two Stanley Cup Playoff games; he was credited with the game-winner in the Flyers 5-2 victory against the New York Rangers in Game 6 of their Eastern Conference First Round series.
In parts of four NHL seasons with the Flyers, Gustafsson six goals, 23 points and a plus-17 rating in 91 games. He had two goals and an assist in nine Stanley Cup Playoff games.