Michael Del Zotto will miss four to five weeks with an apparent knee injury, weakening the Flyers' defense but making it easier for general manager Ron Hextall to assemble the opening-night roster.

Del Zotto, a slick puck-mover who is one of the team's top defensemen, played nearly 17 minutes in the Flyers' 4-2 exhibition win over the New York Rangers Thursday and seemed fine as he joked with teammates after the game.

But he suffered an injury late in the game and it wasn't diagnosed until Friday.

When coach Dave Hakstol was asked about Del Zotto missing Friday's practice in Voorhees, he referred the question to Hextall.

It was an ominous sign.

About two hours later, Hextall released a statement saying Del Zotto would be sidelined at least a month. As is his custom, Hextall did not give injury specifics. CSN said it was a left knee injury.

Del Zotto, 26, was limited to just 52 games because of season-ending wrist surgery last February. Earlier in the week, Del Zotto said his wrist felt 100 percent and that he was excited for the season.

"Health-wise, I'm great," he said at the time. "I haven't had any restrictions or any setbacks."

Now he is battling another injury.

Del Zotto, who can become an unrestricted free agent in July, is expected to be put on the long-term injured reserve , which would give the Flyers salary-cap relief of $3.875 million.

That would enable them to easily fit under the $73 million cap.

Before Del Zotto's injury, Hextall was in a difficult cap position - and it appeared he would have to make roster trims that accounted for at least $1.675 million in cap dollars.

The injury leaves the Flyers with six healthy defensemen. At Friday's practice, these were the pairings: Shayne Gostisbehere and Andrew MacDonald; Mark Streit and Ivan Provorov; Nick Schultz and Radko Gudas.

That could be the grouping for Friday's opener in Los Angeles.

Brandon Manning, who is nursing a shoulder injury, skated at Friday's practice but wasn't allowed to absorb contract. He said he will be on the Flyers' season-opening road trip but didn't know if he would be healthy enough to play, if needed.

If Manning isn't healthy, the Flyers might recall a Phantoms defenseman such as T.J. Brennan or Sam Morin as insurance.

In an indirect way, Del Zotto's injury helps Roman Lyubimov and Nick Cousins, forwards who have had strong camps but were among the candidates to be sent to the minors to make the team cap-compliant.

Both are now expected to start the season with the Flyers. Hextall doesn't have to hand in his roster until Tuesday at 5 p.m.

The Flyers, who finish their preseason schedule Saturday evening in Boston, must cut a forward to get down to 23 players.

Matt Read, Chris VandeVelde and Jordan Weal are among the candidates to be trimmed. Weal, 24, has had the best camp of the trio, and if he was put on waivers in an attempt to send him to the Phantoms, another team might grab him.

Read, coming off consecutive disappointing seasons, has played in just two preseason games.

If the Flyers send Read to the Phantoms - assuming he cleared waivers - the Flyers would get $950,000 in cap relief from his $3.625 million cap hit. If that happened, the Flyers would hope the demotion might recharge the veteran winger, like it did MacDonald last season, when the defenseman replaced the injured Del Zotto and helped the Flyers earn a playoff berth.

scarchidi@phillynews.com

@BroadStBull www.philly.com/flyersblog