Kapanen vanished during the Carolina Hurricanes' magical run to the finals last season, scoring just one goal in 23 postseason games. He doubled his output from last year's playoffs in this one to help put the Flyers one win from advancing to the conference semifinals.
"It has been a tough 12 months," Kapanen said. "My offensive struggle pretty much started last year in the playoffs and it carried throughout the season this year. My numbers weren't what they were last year. Being an offensive player and not putting numbers on the board, I was starting to press. Hopefully, these goals will relax me."
After Wednesday night's triple-overtime marathon, defenseman Aki Berg gave Toronto a lead 2 1/2 minutes into the game with his first career playoff tally. But the Flyers responded with goals 1:55 apart late in the first period and never looked back.
Former Maple Leaf Dmitry Yushkevich and Simon Gagne also tallied for Philadelphia, which lost defenseman Eric Desjardins to a foot injury midway through the third.
Game 6 will be played Monday night in Toronto.
With Philadelphia applying early pressure, Darcy Tucker broke out of his own zone to lead a three-on-two rush against Roman Cechmanek.
Travis Green took a feed from Tucker before dishing to Berg, who unleashed a slap shot from the left faceoff circle that beat Cechmanek at 2:34 for his first tally in 42 postseason games.
It was the first shot of the game after the teams combined for 113 in Game 4.
Defenseman Chris Therien thwarted another Toronto scoring chance, breaking up a two on one midway through the first, before the Flyers capitalized on a power-play opportunity to tie it.
With Tucker in the penalty box for closing his hand on the puck, defenseman Kim Johnsson fired a shot from the left point that Kapanen deflected between teammate Jeremy Roenick's legs and past a screened Ed Belfour at 14:30 for his first playoff tally since Game 4 of last year's conference finals against Toronto.
"I was in front of the net on the power play and I ended up just getting the stick on that one," Kapanen said. "Johnsson shot and it went off my stick."
Less than two minutes later, Philadelphia took advantage of a turnover to grab the lead.
The hero of Game 3 with his double-overtime goal, Leafs defenseman Tomas Kaberle coughed up the puck behind his own net. Roenick pounced on it and fed Yushkevich, whose shot from the slot beat Belfour low to the glove side at 16:25.
"I was just happy to score a goal in the playoffs," Yushkevich said. "It's not like it was a game-winning goal. I was just happy to score that goal. Jeremy and Tony did a great job in the corner and they got the puck away from the Toronto defense.
"Their forwards collapsed down low to help their defense. The slot was wide open and JR saw me. He's such a great player that I didn't have to yell."
"I tried to handle the puck and it ended up in our net," Kaberle said. "It ended up being the turning point of the game. It's tough. What I have to do is think about the next game and forget about this one."
Kaberle's coach agreed with his assessment of the goal.
"What tires you out is when you give up simple goals. That tires anybody out," Pat Quinn said. "The power-play goal was one of those ones that goes in, but the penalty was just atrocious. We can't have those kind of penalties. The second goal, I can pick the guy and say, `What the hell was he thinking?'"
Tucker nearly evened the contest after Mark Recchi was stopped in front by Belfour, but his shot with 2:15 left in the period hit the right goalpost.
"We hit a couple of posts that could have made it 2-2 or 3-2 for us," Tucker said. "Those bounces in playoff hockey are what counts. Sometimes, when you want to win a championship, you have to have some luck and right now, we're not creating some luck."