The penalty shot was awarded after Islanders defenseman Calvin de Haan was called for closing his hand on the puck in the crease. Barkov was chosen by Panthers coach Gerard Gallant among the players on the ice during the play.
"I didn't know that they were going to call a penalty shot," Barkov said. "I didn't know the rule, but then Coach said I'll go shoot. I was pretty confident. I wasn't nervous, but sad that it didn't go in."
Greiss said he also wasn't nervous when the penalty shot was awarded at 7:19 of the first overtime.
"I was surprised they called it there," he said. "I always try my same game plan on a penalty shot. I'm lucky I got it."
It was the first overtime penalty shot in the postseason since 1998. All three attempts were unsuccessful.
Washington Capitals forward Joe Juneau was stopped by Pittsburgh Penguins goalie Ken Wregget in 1996, and Andy Moog of the Montreal Canadiens stopped Penguins forward Aleksey Morozov in 1998. Panthers forward Jaromir Jagr, the oldest player in the NHL at 44, played in all three games.
De Haan said he didn't think he had violated any rules.
"I'm pretty sure the rule is you've got to cover the puck in the crease in order for the other team to get a penalty shot," de Hann said. "I technically didn't cover it. It's not like I can bounce the puck like a soccer ball off the chest. I can't control it off my chest. I'm trying to play it when there's five guys trying to score.
"It's just a reactionary thing. Thomas bailed me out for sure."
Barkov scored on a variety of moves in the shootout during the regular season, and the Panthers were confident he would deliver again.
"It's a tough situation," Florida defenseman Brian Campbell said. "It's a lot of pressure on him. But that's the guy you want going. His record is pretty good. He had to pick somebody on the ice. I think he's the right guy to pick obviously. It's just a tough break .
"I don't know what the read was and everything, but it's a tough bounce for us."
