Leighton has a bulging disc in his back and it was originally thought he could return by the end of the month. General manager Paul Holmgren says Leighton will have surgery on Monday.
Leighton was strong during last year's postseason and helped the Flyers make a surprise run to the Stanley Cup finals. He went 8-3 with a 2.56 goals-against average in 14 playoffs games and set a team playoff record with three shutouts as Philadelphia won its first Eastern Conference championship since 1997.
Flyers rookie Sergei Bobrovsky stopped 29 shots in his first NHL game in a 3-2 win over the Pittsburgh Penguins on Thursday night.