Dallas wasn't counting on production from Tomas Vincour, too.
Vincour scored his fifth NHL goal in the final minute of regulation, and then added the lone goal of the shootout in the fifth round to give the Stars a 4-3 victory over the San Jose Sharks on Thursday night.
Lehtonen made 45 saves through overtime and then was perfect in the shootout. He stopped Logan Couture in the final round to seal the win for Dallas.
Vincour gave the Stars the edge in the tiebreaker when he flipped a backhander past Antti Niemi in his second career shootout attempt, netting his first shootout goal.
"(We found) a new player to finish these games in (Vincour) with a great goal, and then the other goal in the shootout," Lehtonen said.
Although he has almost no shootout experience in the NHL, Vincour wasn't overwhelmed when he was picked by Stars coach Glen Gulutzan.
Vincour had several shootout attempts last season when he played for the AHL Texas Stars, Dallas' primary minor league club, then coached by Gulutzan.
"(Gulutzan) put me out there against Buffalo, too, when we played there on the road (this season), and last year I scored a few goals in the shootout, so I wasn't surprised," Vincour said. "I knew what I wanted to do before I went out there. I just went on the ice and knew that I was going to go backhand."
Pacific Division-leading Dallas won its fourth straight and improved to 79 points, four ahead of San Jose.
Joe Pavelski put the Sharks in front 3-2 when he pushed a rebound past Lehtonen with 3:32 left in regulation for his 24th goal. But with Lehtonen off for an extra skater, Vincour nudged the puck over the line at 19:45 to tie it. The goal was upheld by video replay.
"We just can't give up that last goal," Pavelski said. "There definitely was some good out there, but it's tough to accept when you don't get two points. We've got to find a way to win."
Pavelski had the best scoring chance in overtime, while the Sharks were on a power play, but Lehtonen denied his backhanded attempt from in close with just under 90 seconds to play.
Joe Thornton had three assists, and Niemi made 32 saves for the faltering Sharks, 2-7-3 in their last 12 games overall and 1-5-2 in their last eight on the road.
"The giveback, the loss of a point is what's affecting us right now. We're down about that," Sharks coach Todd McLellan said of the late blown lead.
Dallas returned from a 3-0 road trip and is 8-0-1 in its last nine.
Patrick Marleau notched his 27th goal of the season from the slot 25 seconds into the third period to put the Sharks ahead 2-1.
But Jamie Benn's 20th drew Dallas even at 2 at 6:42 of the third. He backhanded a pass from Adam Burish past Niemi.
The Stars took the lead when Ryder netted his 29th goal at 12:16 of the second, but Torrey Mitchell tied it at 3 when he got around defenseman Alex Goligoski and beat Lehtonen from close range with 1.6 seconds remaining in the second period.
The Sharks opened a four-game trip with the fourth of six meetings with the Stars. San Jose won the first three by a total score of 14-5, although the Stars used backup goalies in all of those games while Lehtonen was rested or injured.
Beating San Jose for the first time this season stoked the Stars' confidence.
"It gives us a little bit of a boost," Gulutzan said. "There's no question they've had our number, but for coming back from the road, we played a pretty good game. I think we gave up a lot, but remember, they're a little bit of a wounded bear too right now, so it's not an easy game against them."
Dallas held an early 7-4 edge in shots, but San Jose finished with a 16-8 advantage in the scoreless opening period.
Ryder had given the Stars the lead when he skated in alone and fired a shot past Niemi. Seconds earlier, Lehtonen had denied Ryane Clowe's prime scoring chance with a sliding pad save.
Dallas D Sheldon Souray was done after two periods because of an undisclosed lower body injury. ... Sharks RW Martin Havlat (hamstring) missed his 36th consecutive game. ... Lehtonen has started 16 of 18 games. ... LW Steve Ott (back spasms), LW Brenden Morrow (neck, shoulder) and C Jake Dowell (finger) were out for Dallas. Ott missed his first game since Nov. 15. Morrow, the Stars captain, sat out his 18th straight game, but he is practicing with the team and is nearing a return to the lineup.