With 4:43 left in the second period, Washington's Tom Wilson leveled Schenn and the center's head crashed into the boards. A woozy Schenn fell three times on the ice and was helped to the locker room. Wilson was penalized five minutes for charging, five minutes for fighting Nick Grossmann, and a game misconduct.
The Flyers capitalized on the extended power play, getting goals from Mark Streit - his shot hit the inside of the left post and caromed into the net - and Jake Voracek late in the second period.
The coaches had different views of Wilson's hit, which is expected to be reviewed by the NHL.
"It's a reckless play, getting hit from behind like that," Flyers coach Craig Berube said. (As for Schenn, Berube said, "I think he's OK.")
Capitals coach Adam Oates called it a "clean hit" and said he didn't think Wilson deserved to be penalized for the check, which Voracek called an "ugly hit."
"We didn't want to see our teammate, our friend, go down like that," Voracek said.
Voracek scored the Flyers' first and last goals of the period, sandwiched around goals by Matt Read and Streit.
Schenn did not return to the game, and the Flyers said only that he had an upper-body injury. The Flyers are already missing Vinny Lecavalier (non-displaced back fracture), who had been their second-line center.
The Flyers had a 4-1 lead with less than nine minutes left in Sunday's 5-4 shootout loss in Washington.
"The guys are hungry to get back and play," said Berube before the game. He turned 48 on Tuesday.
Wayne Simmonds, converting a John Carlson turnover, gave the Flyers a 5-2 lead with 12:31 left in the third period. That gave the Flyers four consecutive goals.
Unlike Sunday, they did not crumble late in the game.
"The guys talked about not letting that happen again," Read said. "We were amped up."
"We learned the hard way," captain Claude Giroux said.
After his late turnover helped send the Flyers to Sunday's gut-wrenching loss, Flyers goalie Steve Mason wanted a chance to redeem himself. He got it.
Mason failed on a clearing attempt Tuesday and it led to Alex Ovechkin's 399th career goal 40 seconds into the second period, giving the Capitals a 1-0 lead. But the 25-year-old goalie regrouped and made 24 saves, improving to 12-9-4.
"You just have to make sure you're stopping the next one and build off the following saves," Mason said. "They had a couple quick goals there, but the guys really responded."
The Flyers, winners of seven straight at home, will try to go over .500 for the first time this season Thursday when they host Mason's former team, Columbus.