Zajac reportedly twisted his right ankle at practice Friday. According to The (Bergen) Record, he tripped and fell during the early stages and was replaced by Jacob Josefson on a line with Dainius Zubrus and Damien Brunner.
Zajac told The Record he "caught a rut" and his falling was "laughable."
In 12 games this season, Zajac has one goal, four points and a minus-5 rating. He missed all but 15 regular-season games in 2011-12 after tearing his left Achilles tendon that summer; in 75 regular-season games since returning from that injury, Zajac has 10 goals and 30 points.
Goalie Cory Schneider practiced for the second straight day and appears ready to be the backup to Martin Brodeur against the Flyers. He likely will start on the road against the Minnesota Wild on Sunday. Schneider sustained a lower-body injury Oct. 24 and has missed the past two games.