Van Riemsdyk, hindered by injuries that general manager Paul Holmgren said are not serious, has struggled through most of the season.
On Thursday, playing on a new line with Brayden Schenn and Wayne Simmonds, he resembled the player who was dominant in last year's playoffs.
"It was JVR's best game," coach Peter Laviolette said. "I liked the fact he was skating to be physical. He banged bodies out there. I always think that if you want to get yourself into the game, get your feet moving and go bang somebody because it always puts you around the puck."
Van Riemsdyk, 22, admitted he has been pressing.
"I don't think I've felt as comfortable or confident as I had last year. I think I'm still working toward that, for whatever reason," he said.
Before Thursday, the last time the Blackhawks were in town, Kane was scoring the Strangest Goal to Ever Win a Stanley Cup.
On Thursday, Kane - drafted No. 1 overall, just ahead of van Riemsdyk, in 2007 - scored from the slot to tie the game at 4 with 5 minutes, 20 seconds to play.
Until the last six minutes, the Flyers controlled the game. But seconds after Hartnell's tip-in hit the post, Brent Seabrook scored from the right circle, getting Chicago to within 4-3 with 5:45 left. Just 25 seconds later, after Jonathan Toews stripped the puck from Marc-Andre Bourdon, Kane scored his 10th of the season to tie the game for the last time.
Kimmo Timonen, the Flyers' star defenseman, left the game in the second period with what was believed to be a wrist injury.
The Flyers had no minor penalties, got goals from all four lines, and totaled 46 shots - seven by the ever-present Hartnell (two points) - in what was the fastest-paced game of their season.
The Flyers had lost five of their last seven, including the Winter Classic on Monday, when they blew a 2-0 lead and lost to the Rangers, 3-2.
The Flyers scored three goals in a stunning 4:20 span to take a 4-2, second-period lead. Hartnell, rookie Harry Zolnierczyk, and van Riemsdyk were the goal scorers, the latter two on rebounds.
Chicago had briefly taken a 2-1 lead as Andrew Shaw, who was beaten and bloodied in a first-period fight with Zac Rinaldo, was patched up before scoring with 12:23 left in the second period.
Seventeen seconds later, Hartnell swatted Claude Giroux's pass out of the air - it was a few inches off the ice - and beat ex-Flyer Ray Emery from the slot, tying the game at 2. It was Hartnell's 18th goal, tying him for the team lead with Giroux (two assists), and it gave him points in seven straight games.
Zolnierczyk and van Riemsdyk then scored 23 seconds apart, increasing the lead to 4-2. The Flyers had 21 shots in the second period, equaling their season high for any period.
After sitting out two games, Ilya Bryzgalov returned to the nets. He has been spending extra time with goaltending coach Jeff Reese to fix some mechanical flaws.
"He's going to get his confidence back, and he's going to be a major cog for us," Danny Briere said before the game.
Bryzgalov was steady until the Blackhawks' two late goals; he said he was ill after the game and declined to speak to reporters.
Contact staff writer Sam Carchidi at firstname.lastname@example.org or @BroadStBull on Twitter.