Anthony Beauvillier says the New York Islanders had no doubt they would overturn a two-goal deficit to defeat the Tampa Bay Lightning and force a Game 7 decider in their Stanley Cup semifinal series.

Things were looking cosy for the Lightning as Brayden Point scored for an impressive ninth straight game, while Anthony Cirelli registered an assist and a goal – the only blot to that point being the loss of playoff-scoring leader Nikita Kucherov to injury in the first period.

Staring down the barrel of defeat, Jordan Eberle started New York's recovery late in the second period and Scott Mayfield levelled it up with eight minutes and 44 seconds remaining in the third with an effort that went in off the crossbar.

Beauvillier was then the hero with a first career overtime goal that proved enough for the Islanders to force a deciding game, producing an impressive response to an 8-0 loss in Game 5.

"We knew we were going to bounce back," Beauvillier said. 

"Even going down 2-0, I thought we were still on top of our game. We were having good shifts and we just stuck with it. Obviously a huge character win."

Islanders' star center Mathew Barzal said the team was relaxed despite the perilous situation.

"We knew we had a lot of time on the clock still," he added. 

"Just stuck with it and fortunate enough to get two goals and tie it up, and obviously win in overtime."

The Islanders are set to move to a new venue at UBS Arena next season and with this potentially their last at Nassau Coliseum, spectators celebrated by launching beer cans and bottles onto the rink.

"I've never seen anything like that. A little dangerous, but you don't see that too often, so we embraced it," Barzal said.

"That's the Islanders faithful – they're passionate, they get excited, and it was good stuff."

The two sides will lock horns one last time in the series in Friday's decider in Tampa.