OTTAWA -- The Dallas Stars had to battle to the very end to claim victory after blowing a pair of leads, including giving up the tying goal to the Ottawa Senators with less than 10 seconds remaining in the third period.
Benn scored on Dallas' second attempt in the tiebreaker on Robin Lehner, who replaced an injured Craig Anderson early in overtime.
Ottawa's Bobby Ryan scored the tying goal with 9.6 seconds left in the third period to send the game to overtime. The Senators scored twice in the second to overcome a 2-0 deficit.
"We're going to have to learn how to win, and again, we made it tough on ourselves," Dallas coach Lindy Ruff said. "We're going to have to fix a few of those mistakes we made and get a greater understanding of when you're up 2-0 in a game what kind of opportunities you want to give up and how hard you want to try to score.
"We just gave up a 2-on-1 on the power play and we gave up a 3-on-1 right after that. It wasn't from lack of trying, but our smarts weren't good enough."
With Anderson on the bench for an extra attacker, Ryan broke his stick on a shot from the slot when he beat Lehtonen to even it at three after taking Milan Michalek's centering pass from behind the net.
"I wasn't able to see the puck coming, so I was kind of guessing, maybe he's going right blocker, and maybe he was, but his stick broke and it just kind of trickled in," said Lehtonen, who stopped 33 shots in regulation and overtime. "We just have to be a little sharper, everybody on the ice at that point. It looked great, 20 seconds left and we had the puck and they couldn't pull the goalie, then it all changed quickly."
Anderson left the game at 1:44 of overtime after he was run over by Stars rookie Valeri Nichushkin. The Ottawa goalie was taken off on a stretcher, but gave a thumb's up and a wave to fans at Canadian Tire Centre.
"It's scary," Ryan said. "It's one of those plays that I think it's even worse when you see the replay and the way he kind of got jammed in there. You never want to see it, but it's just a kid going to the net hard and you can't really do anything about it, but it's certainly in the back of your mind for the next four minutes, whatever it was."
Anderson had made 33 saves when he was replaced by Lehner, who stopped both of the shots he faced in overtime.
Senators coach Paul MacLean said that Anderson had a stiff neck and would be evaluated further, but otherwise was fine. He did not expect that Anderson would be available to play Tuesday against the Columbus Blue Jackets.
Antoine Roussel scored an unassisted goal at 3:11 of the third period to put Dallas ahead 3-2. Roussel got credit for his first goal of the season after Ottawa rookie defenseman Mark Borowiecki, who made his season debut, put the puck past Anderson into his own net while trying to clear the crease.
"You feel for him, I think, more than the other guys in the room because he's coming up and it's his first game," Ryan said. "I thought he played really well. I thought his hit there in the second kind of generated some of what we did there in the second, so the guys had his back.
"It's one of those plays where you can't find the hole to hide in big enough and we told him to shake it off and he did, and he came back and responded. You can't really get mad at a guy for that. That's just an honest mistake."
Borowiecki, who played eight games with the Senators over the last two seasons, expressed his gratitude to Ryan for sending the game to overtime.
"I went and gave him a tap after," Borowiecki said. "I told him I owe him a beer, so I think all the guys feel for you on a play like that."
Ray Whitney scored his first goal of the season for Dallas at 17:03 of the first period. Nichushkin made it a 2-0 with his first NHL goal at the 30-second mark of the second.
Erik Karlsson and Jason Spezza tied it with goals later in the second for the Senators, whose winless streak reached a season-high five games (0-3-2).
"It's frustrating when you give up leads like that," Whitney said. "We've done it a couple of times now in the year and part of growing as a group and growing as a team, especially when you're young, is trying to play with the lead, and at times we've done a job of it, and at times we haven't.
"And tonight, we actually did a not-bad job until that, obviously, until that last three or four minutes. They turned it up and had some good chances, but Kari's been there and he was great again [Sunday]."
Dallas outshot Ottawa 19-9 in the first, including Benn's scoring chance off a set-up from Nichushkin 28 seconds after the opening faceoff. A video review upheld the on-ice ruling that Anderson had kept the puck from crossing the goal line.
Senators defenseman Jared Cowen was caught pinching on the Stars' opening goal. Whitney drove the right side and fired a slap shot over Anderson's left shoulder into the top right corner.
Ottawa defenseman Chris Phillips was also caught up ice on Dallas' second goal, following through on a check on Benn along the boards. Nichushkin took Brenden Dillon's drop pass and beat Anderson with a wrist shot from the top of the right faceoff circle.
Karlsson scored on a 3-on-1 at 7:41 of the second period to draw Ottawa to within 2-1. The Senators had successfully killed off Chris Neil's double minor moments earlier when Kyle Turris sent Ryan away on a break down the ice with Karlsson and only defenseman Stephane Robidas back for Dallas.
Ryan passed as Robidas sprawled to the ice to block and Karlsson snapped a one-timer past Lehtonen for his fourth goal.
Karlsson got his second point of the period with an assist on Spezza's goal. Turris took Karlsson's pass and drove a slap shot from the left point that struck the end boards and bounced out front to Spezza, who evened it at two with his eighth goal.
Nichushkin showed his standout speed early with a rush from his zone through the middle that he turned into a breakaway as he blew past Patrick Wiercioch, who took a hooking penalty on the play at 12:41 of the first for his second minor of the opening period after Anderson turned aside the 18-year-old Russian.
Borowiecki dished out a couple of solid hits in the second, including an open-ice hit on Nichushkin as he entered the Ottawa zone that sent the rookie's stick flying.
Dallas left wing Ryan Garbutt returned after serving his five-game suspension for an illegal hit on Dustin Penner of the Anaheim Ducks.
David Johnston, Canada's Governor General, was on hand for the Senators' 10th annual Armed Forces Appreciation Day. Johnston was in full military dress as he dropped the puck between team captains Benn and Spezza for the ceremonial opening faceoff.
About 3,000 Canadian armed forces personnel were among the crowd of 18,106 on hand for the game.