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.
We don't have any excuses tonight. Excuses are for losers. We've played with five defensemen before and it didn't affect us. We just had a bad second period and it cost us the game. We have to look in the mirror and blame ourselves.
— Bruins coach Claude Julien on his team's play with the loss of defenseman Johnny Boychuk