The Islanders advance to play the Tampa Bay Lightning in the Eastern Conference Final, with Game 1 of that best-of-7 series at Rogers Place in Edmonton on Monday (8 p.m. ET; NBCSN, SN, CBC, TVAS). It's the first time New York has reached a conference final since 1993.
"I liked the way we played, I liked our mentality today and we stayed to our identity," Islanders coach Barry Trotz said. "We wanted to play well on the right side of people and we got contributions through the lineup. Obviously, two defensemen scored, some really good plays, good goaltending, and our special teams were pretty good. You have a chance to win when you play like that."
WATCH: [All Islanders vs. Flyers highlights]
Greiss replaced Semyon Varlamov, who started 14 of the Islanders' first 15 postseason games (Greiss started Game 4 against the Flyers).
"It was an unreal game, best game I've seen the team play," Greiss said after his first Stanley Cup Playoff Game 7. "They took most of the stuff away. Happy we got the win here."
Carter Hart made 22 saves for Philadelphia, the No. 1 seed.
"Game 5, Game 6 we got the job done, we were able to get some big goals, play the right way," Flyers forward Claude Giroux said. "Game 7 wasn't the case."
Varlamov allowed nine goals in the past two games, each an overtime loss that prevented New York from ending the series.
"The last two games they got to [Varlamov] a little bit in terms of that, and he's played a lot of great hockey for us," Trotz said. "I wanted the freshness. ... I also knew that with 'Greisser,' just his demeanor, that he'd be a good choice for us. We've been blessed with two goalies. You try to ride the hot guy as long as you can, and if you have to go to the next guy, you do that."
Brock Nelson had a goal and two assists, and Scott Mayfield, Andy Greene and Anthony Beauvillier scored for New York, the No. 6 seed.