Hartnell, an All-Star last season, was injured by a shot taken by teammate Kimmo Timonen in Tuesday's game against New Jersey. Flyers general manager Paul Holmgren made the announcement before Thursday night's game against the New York Rangers.
Hartnell had one point in three games. He led the Flyers with 37 goals last season and had 67 points.
The Flyers are still without forward Danny Briere (broken left wrist). Holmgren says it's 50-50 Briere will be available for this weekend's games at Florida and Tampa Bay.
It's not just going to happen on its own. We have to have guys commit to the areas we need to improve on. We're going to be better than last year but there is still a long way to go. But I really like the pieces and where we're headed.
— Sabres forward Tyler Ennis on the progress of Buffalo's rebuilding process
TONIGHT ON NHL NETWORK
7:00 ET: Day That Changed Game: Roy Trade 8:00 ET: Gordie Howe Special