Fedoruk took on Orr inside the circle to the left of Flyers goalie Antero Niittymaki and exchanged blows with New York's leading fighter. Orr landed a hard, overhand right to Fedoruk's left cheek that sent the Philadelphia player down and out on his back.
Officials immediately summoned the Flyers' medical personnel to the ice, and a stretcher was brought out moments later. Fedoruk appeared to blink and talk, and he made an OK gesture with his fingers as he was strapped to a backboard, and a brace was affixed to his head.
He was taken to St. Vincent's Hospital for observation.
The game was delayed about 10 minutes.
Fedoruk missed 18 games earlier this season after he underwent major facial surgery following an Oct. 27 fight with Minnesota's Derek Boogaard. Fedoruk, who was with Anaheim at the time, was traded to Philadelphia on Nov. 13. He had been wearing a face shield until February.
It was Fedoruk's fifth fight since returning to the lineup Dec. 2.
Fedoruk got into a dustup on Tuesday when he collided with Florida goalie Ed Belfour. When Belfour fell backward, he struck Fedoruk in the head with his stick.
Moments after Orr left the penalty box, he took on Philadelphia's Ben Eager, who knocked Orr to his knees with a punch in the short fight.
New York coach Tom Renney left Orr out of the lineup when the teams last met on Feb. 17 and said he regretted it after Fedoruk and Eager combined for four roughing penalties and a misconduct in the first period. Sean Avery fought Philadelphia's Mike Richards midway through the period of that game.
That contest is best remembered for the violent accidental collision between Flyers forward Mike Knuble and New York's Brendan Shanahan that left Shanahan unconscious on the ice. He was also removed on a stretcher and missed 15 games before returning for Wednesday's rematch with Philadelphia.
Knuble, who had surgery to repair a broken cheekbone and orbital bone following the collision, played in his fourth game since recovering from the injury.