It is believed that Leighton, who was unavailable for comment Monday, originally strained his back while working out over the summer.
The 29-year-old aggravated the injury in the third period Friday. He was removed after the overtime session and replaced by backup Brian Boucher for the shoot-out.
Flyers coach Peter Laviolette would not disclose the possible replacement for Leighton. Nor would he name the starter for Tuesday's exhibition game against the New Jersey Devils in Newark, N.J. Boucher and newcomer Sergei Bobrovsky are the candidates.
Bobrovsky has been a pleasant surprise this preseason. Laviolette said he had played well enough to get another exhibition start. He started Saturday's 3-2 shoot-out victory at the Minnesota Wild, stopping all three of the Wild's shoot-out attempts after making 18 saves in regulation.
While Holmgren agreed that Bobrovsky has been impressive, he said he did not think the 6-foot-2, 190-pounder was ready to become a regular starter.
"I think that's a little bit of a stretch," Holmgren said. "But we are going to continue to look at him."
Getting better.Goaltender Johan Backlund and forwards Blair Betts and Ville Leino could play in their first preseason games later this week.
Monday was Backlund's first full practice with the team after recovering from off-season hip surgery. Betts (off-season shoulder surgery) and Leino (off-season hip surgery) participated in contract drills for the first time Monday.
The two forwards are expected to play in exhibition games later this week.
"The plan now is to try to get [Backlund] a game here coming up toward the end of the week and see how he does," Holmgren said. "He's a little bit behind because he hasn't been able to take part in full practice. But health-wise, he's been cleared to do everything."
Holmgren said defenseman Chris Pronger would be ready to play at the beginning of the regular season. The Flyers open in Pittsburgh against the Penguins on Oct. 7.
Pronger (off-season knee surgery) donned a yellow noncontact jersey at Monday's practice.
Taking it to the wire. The Flyers head into Tuesday's exhibition game with a 3-0-1 preseason record. All four of those games were decided by a shoot-out.
Contact staff writer Keith Pompey at 610-313-8029 or firstname.lastname@example.org.