"That was huge," said Jake Voracek. "A guy gets out of the box and scores a big goal. That's huge."
As slick as the 25-year-old defenseman looked on the play, Gustafsson's pivotal goal made coach Craig Berube look even better.
In the most important game of his brief coaching career, Berube opted for Gustafsson over Hal Gill, a 39-year-old veteran with 111 playoff games under his pads.
Gustafsson hasn't played that many games in his NHL career and had seen action in only seven postseason contests, none since 2012.
The decision became necessary when defenseman Nick Grossman was hurt in Game 4. Berube went with Gill on Sunday in the Flyers' Game 5 loss at Madison Square Garden, and he was on the ice for two of New York's four goals.
"Obviously, I was a little disappointed I didn't get to play last game," Gustafsson said. "He [Berube] had his reasoning, and I accepted that. When I was told that I was playing tonight, I couldn't tell you how excited I was."
In the 2012 playoffs, Gustafsson scored a goal in the series-clinching victory over Pittsburgh. Overall, he had a plus-3 rating against the Penguins.
That wasn't a fluke. This season, though he played in only 31 games, Gustafsson had the best plus-minus rating of any Flyers defenseman, plus-7.
In the second period, Gustafsson's stick got briefly entangled with Rangers forward Derek Dorsett's as they chased a loose puck alongside Flyers goalie Steve Mason. Referee Dean Morton's whistle - and the big-screen replays - provoked an angry reaction from the boisterous and frequently profane crowd.
All was forgotten when the penalty expired and Gustafsson broke free.
"I got out, and Cob saw me," he said. "Lundqvist was kind of going for the puck too. But it kind of stopped for me and I shot it [through the] five hole."