Paired with veteran Matt Carle, the speedy Gustafsson played 22 minutes, 9 seconds and was plus-3, spending a lot of time annoying Crosby (minus-3).
"I can't even describe how I feel. I feel so happy, and to seal it at home makes it that much better," said Gustafsson, 23. "The crowd was unbelievable today. . . . I've been on a high since I got here."
It's been a strange season for the 5-foot-10, 180-pound Gustafsson, an always-smiling Swede who impressed the Flyers' brass before being sidelined by wrist surgery on Nov. 17. After a six-week recovery period, Gustafsson played with the AHL's Phantoms before returning to the Flyers' lineup in mid-January.
That started his back-and-forth journey between Philadelphia and Adirondack.
"Every time Gus got sent back to the minors, I always said that it wasn't about his play," coach Peter Laviolette said. "He never got sent back because he couldn't cut it here or he couldn't do it. We had numbers and depth at the time, and based on injuries right now and where we're at, Gus had an opportunity to step in today."
"Outstanding" is how Laviolette described Gustafsson's defensive work Sunday.
"A lot of times it was against the Malkins and the Crosbys of the world, and that's not an easy task," Laviolette said.
When Nick Grossmann went down with an apparent concussion, Gustafsson made his NHL playoff debut in Game 5 and played 12 solid minutes in the Flyers' 3-2 loss in Pittsburgh
He made a bigger impact Sunday.
"I just tried to use simple passes and get the puck out of the zone - and keep the forwards to the outside," he said.
As for his hounding of Crosby and Malkin, Gustafsson did a good job denying them time and space.
"I just tried to stay on the inside and let them shoot from the outside," he said. "I think it was a real team effort today. Everyone was supporting each other and backing each other up, and if anything happened, the next guy had your back."
With the Flyers holding a 2-0 lead, Gustafsson skated through the neutral zone and, instead of feeding snipers Claude Giroux or Jaromir Jagr, fired a wrist shot from above the left circle that eluded shaky goalie Marc-Andre Fleury.
"I think it dipped a little bit. I think it shocked him," said Gustafsson, laughing. "I didn't think he expected me to shoot it. I had Jags and G on both sides, but I figured I was just going to put it on the net and see what happens. I was kind of tired and I wanted to get off, and it worked out pretty good."
"To score a big goal like that, it was huge for him," winger Scott Hartnell said. "He's not the biggest guy. He's a lot like Kimmo [Timonen], with how good of position he's always in. His stick is always in the right place."
Carle said Gustafsson, one of five rookies in the Flyers' lineup, played with poise "beyond his years."
During the regular season, Gustafsson had a goal, four assists, and a plus-12 rating in 30 games with the Flyers.
"It's tough to come into a series like that," said Carle, who spent some time paired with Gustafsson in the regular season. "He knows what to expect at this level, but when you come into a playoff atmosphere, it's a little bit faster, a little bit more intense. He just makes a lot of little plays that a lot of people don't notice. His panic level is low, and he made a really good play on that goal - taking the ice that was given."
And making his first home playoff game a memorable one.
Contact Sam Carchidi at firstname.lastname@example.org or follow @BroadStBull on Twitter.