PHILADELPHIA — It was a priceless performance without their $100 million superstar.

The Devils insisted they weren’t worried about the loss of Ilya Kovalchuk with a back injury. They felt they could win without him.

It may, however, have taken them two periods last night to truly start believing.

“With Kovy being out and as big a part of our team as he is — I think internally, without anybody even needing to say anything — we all knew we needed to be better to fill that void. And we did that,” captain Zach Parise said.

In what may ultimately go down as another historic night in which they stunned the Philadelphia Flyers, the Devils erupted for four goals in the third period for a 4-1 victory that actually silenced the boisterous crowd at the Wells Fargo Center.

The Game 2 triumph, which saw rookie defenseman Adam Larsson score a goal in his Stanley Cup playoffs debut and David Clarkson follow with the winner, evened the Eastern Conference semifinal series, 1-1. Game 3 will be played at the Prudential Center Thursday night.

“I think we know the hole we’re in if we lose tonight. Our backs are against the wall with Kovy out and I’m not surprised that we responded the way we did,” Devils coach Pete DeBoer said.

DeBoer said he never doubted his players.

Flyers-Devils Game 2 (Gallery 1), May 1, 2012 33 Gallery: Flyers-Devils Game 2 (Gallery 1), May 1, 2012

“No, I really felt we would respond like this. It’s not more than I expected. It is what I expected,” he said. “I knew we would be better than Game 1.

“I think there were some obvious reasons why we ran out of gas in Game 1 (a quick turnaround after the seven-game first round), but I knew we’d bounce back. We’ve dealt with the adversity of injuries and things all year. I really felt we’d have a great game and we did.”

Kovalchuk did not accompany the Devils to Philadelphia. Although the team said he has a “lower body injury,” it is actually his back.

The specifics of Kovalchuk’s injury were confirmed by two people familiar with the diagnosis. They requested anonymity because NHL teams rarely, if ever, elaborate on such details — and are not required to by league rules.

Flyers-Devils Game 2 (Gallery 2), May 1, 2012 22 Gallery: Flyers-Devils Game 2 (Gallery 2), May 1, 2012

Despite outshooting the Flyers, 12-2, in the second period, the Devils were behind, 1-0, as the third period began.

Defenseman Marek Zidlicky was sent off at 1:39 for elbowing Eric Wellwood. But it was 4-on-4 13 seconds later when Scott Hartnell was penalized.

DeBoer put Peter Harrold, who spent most of the game as a right winger, on defense alongside Larsson.

“One of our offensive defensemen, Zidlicky, was in the box at the time. It was natural to throw those guys out there,” DeBoer explained. “Great for Larss. He’s a kid who sat for eight games and worked to keep himself in shape. He jumps into a playoff game and does what he does. It says a lot about his character.”

Larsson tied the game as the teams skated four-on-four. Dainius Zubrus battled in front, eventually setting up the 19-year-old Swede for a shot from the right circle that beat Flyers goalie Ilya Bryzgalov on his glove side at 3:08.

Clarkson’s goal at 11:17 gave the Devils the lead. Parise took it to the net and the puck wound up on Clarkson’s stick, where he jammed it in and jumped onto the crossbar.

“It was nice for him to go to the net and score one of his typical goals,” Martin Brodeur said. “Hard-nosed, jump on the crossbar, hold it for a second for pictures ... . He’s got the beard, too. He’s proud of that.”

Clarkson was asked about his celebration.

“You mean my Superman?” he joked. “I got shoved up from behind and ended up on the net.”

Travis Zajac’s wrap-around sealed it at 14:01 before the Flyers pulled Bryzgalov for a 6-on-4 power play and Bryce Salvador scored short-handed from his own end into the empty net.

“Embarrassed? Anytime you score in the playoffs you take it,” Salvador said. “On the score sheet it’s not going to say how it went in. So I’m telling my kids I went top shelf.”

Actually, it does say “empty-net goal” on the score sheet. But in the Devils’ most stunning victory in Philadelphia in a dozen years, they were ready to believe almost anything.

Rich Chere: rchere@starledger.com

More from Game 2:

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Brilliant through first 40 minutes, Flyers goalie was human during third-period onslaught by Devils.

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The Politi column: Clarkson crashes the party and it couldn't have come at a better time for the Devils

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Clarkson on his 'Superman' celebration: "I don't even remember anything, except being on the net when it went in."

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Devils' rookie Adam Larsson makes up for early mistake by scoring his first playoff goal.