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

Carkner fired a slap shot through traffic from the right point that deflected off the Penguins' Matt Cooke for his first goal of the postseason, ending the longest game of the playoffs this year. It was by far the longest game in Senators' history — 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 with 9:36 to play, Mike Fisher and Jarkko Ruutu also scored, and 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.

"It was a huge win," Ottawa coach Cory Clouston said. "I thought the guys showed a lot of character."

Sidney Crosby had a goal and an assist to give him multiple points in every postseason game this season, and Kris Letang and Chris Kunitz also scored for Pittsburgh. The defending Stanley Cup champion 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," Clouston said. "I'm sure the fans like that."

Pascal Leclaire made 56 saves in his first playoff start. He made his career postseason 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.

Nick Foligno nearly won it 2:05 into overtime — but officials ruled he directed the puck into the net off a rebound of a Jason Spezza shot on a 2-on-1 with a kicking motion. Referee Dan O'Halloran immediately waved off the goal — the third initial disallowance of a goal in the game.

The first of which — Chris Kunitz sliding the puck in with the net lifted up its moorings with 1:26 to play in the second period — ultimately counted. But when Kunitz redirected Gonchar's shot from the point while standing in the slot 3:22 into the third, officials signaled Kunitz made contact with the puck when it was above his shoulder.

Crosby scored his fifth goal of the series with 11:59 left in regulation when he fired Malkin's rebound into the large portion of the net that was vacated while Leclaire was sprawling.

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 slap shot from the high slot.

Pittsburgh's best chances after regulation were when Malkin hit a post 5 minutes into the second overtime and then when he was denied by Leclaire about 3 minutes later on a wrist shot.

"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."

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 a Crosby shot. Replays confirmed the pegs remained in the ice and inserted into the bottom of each post.

Ottawa scored first 10:25 in when Karlsson's shot from above the right faceoff circle hit off of the skates of both Fisher and Gonchar and into the net behind Fleury.

Ruutu made it 2-0 just 68 seconds later when he slammed a loose puck in the crease into the net after Foligno made the play from behind the net.

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 at least two points in each of the five playoff games, 13 in total. 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.