PITTSBURGH - Matt Carkner helped the Ottawa Senators avoid elimination in their first-round playoff series and deprived the defending champion Pittsburgh Penguins of at least a few extra days of rest.

Carkner scored at 7:06 of the third overtime to give the Senators a 4-3 victory over Pittsburgh on Thursday night, forcing a sixth game in the Eastern Conference series.

"There's a lot of belief and trust in this room," said the Senators' Matt Cullen, who was creating a screen in front of Marc-Andre Fleury when the winning goal went in. "We maintain a positive attitude and good feeling in here that we're still in it."

The goal to end triple OT

Carkner took a pass from captain Daniel Alfredsson and fired a slapshot through traffic from the right point that deflected off the Penguins' Matt Cooke for his first goal of the post-season, ending the longest game of the playoffs this year at 107 minutes 6 seconds. It was by far the longest game in Senators' history -- and only their second to go past one extra session.

"Three overtimes and we knew it wasn't going to be a pretty goal," Carkner said. "I think it deflected off someone -- I didn't even know how it went in -- but it's just a great feeling right now."

Peter Regin tied it 3-3 with 9:36 to play, while Mike Fisher and Jarkko Ruutu also scored for Ottawa. Jason Spezza and Erik Karlsson each had two assists for the Senators, who have won two of three at Mellon Arena. Game 6 is Saturday night at Ottawa.

"We haven't done anything other than get ourselves back in the series," Cullen said. "It's a big win, and the way we did it was really big and certainly a big boost for us."

Sidney Crosby had a goal and an assist to give him multiple points in every playoff game this year, and Kris Letang and Chris Kunitz also scored for Pittsburgh. The Penguins rallied from a 2-0 deficit to take a 3-2 lead on Crosby's goal with 10:59 left in regulation only to give up the equalizer 1:23 later.

"A lot of drama," Ottawa coach Cory Clouston said. "I'm sure the fans like that."

Leclaire stars in net

Pascal Leclaire made 56 saves in his first playoff start. He made his career post-season debut after Brian Elliott was pulled during the second period of Game 4 and wasn't announced as the starter until Thursday morning.

"He played outstanding," Clouston said. "He was confident, comfortable. I thought he was very square and poised. Boy, did he come through for us."

The game was the second-longest in the history of Mellon Arena (Philadelphia's Keith Primeau scored in the fifth overtime to beat the Penguins on May 4, 2000) and third-longest in Penguins' history.

"Everyone was tired at the end of the game," Letang said.

Nick Foligno nearly won it 2:05 into overtime -- but officials ruled he directed the puck into the net with a kicking motion -- the third initially disallowed goal in the game.

The first of which -- Kunitz sliding the puck in with the net lifted up on its moorings with 1:26 to play in the second period -- ultimately counted. But Kunitz had a goal taken away 3:22 into the third when his deflection of Sergei Gonchar's shot was with his stick above his shoulder.

Sens almost played 'waiting game'

Crosby's goal came from firing a Malkin rebound past a sprawling Leclaire.

With all the momentum at that point -- Pittsburgh had outshot Ottawa 27-9 between its first goal late in the first period until Crosby's goal -- it seemed a mere formality the Penguins would cruise into the second round on a four-game winning streak.

But Regin tied it only 1:23 later on a slapshot from the high slot.

"The last half of the second and the first half of the third, we kind of sat back and it was almost as if we were waiting for something bad to happen," Clouston said. "It wasn't until they went ahead that we started to just play our game."

Pittsburgh's best chances after regulation were when Malkin hit a post five minutes into the second overtime and then when he was denied by Leclaire about three minutes later on a wrist shot.

The Senators had two power plays in overtime and the Penguins one.

"A lot happened (in the overtimes) with penalties and chances and posts, but that's just the way it works out," Crosby said. "Unfortunately, we didn't get it done here, but we've got to find a way to regroup and be ready to go to Ottawa."

Disputed goal

Kunitz's first disputed goal counted with 1:26 left in the second when both sides of the net lifted up simultaneously as he put in a rebound of Crosby's shot. Replays confirmed the pegs remained in the ice and inserted into the bottom of each post.

Ottawa opened the scoring at 10:25 of the first when Karlsson's shot from above the right faceoff circle hit off of the skates of both Fisher and Gonchar and into the net, and Ruutu made it 2-0 just 68 seconds later.

But the Penguins scored the next three, starting with Letang on the power play with 1:55 to play in the first, his second of the series.

"Obviously, you just forget about this and you just have to take advantage of your next chance to finish it," Letang said.

NOTES: Crosby has 13 post-season points. Dating back to the final five games of the regular season, Crosby has 28 points in his past 10 games. ... The Senators improved to 12-11 in overtime in their history, 2-0 when it extends past one overtime and 4-3 at Mellon Arena overall. ... Pittsburgh is 20-16 overall in playoff overtimes, 2-3 when there are multiple overtimes.