Couture's power-play goal 1:20 into overtime was his fifth game-winner of the season, giving the Sharks a 4-3 victory over the Dallas Stars on Thursday night.
"I kind of curled back, gave myself some momentum and just stepped into a wrister," Couture said. "Those are the ones that feel real good coming off your stick."
Sharks coach Todd McLellan has already come to expect big plays from Couture.
"Catalyst would be a very good word," McLellan said. "He's scored some very big goals. Our special teams were below par but he found a way to get the winner in overtime. He's one of the top, if not the top, rookie in the league and when you have that type player on your team, you're thankful."
Lehtonen said he never saw Couture's shot.
"They got some good traffic there, and when I came to the locker room, I went to see it (on replay) because I didn't even know which side it went in," Lehtonen said.
Torrey Mitchell and Devin Setoguchi scored during a 1:46 span in the second period for the Sharks. Setoguchi, activated off injured reserve Wednesday after missing nine games with an upper-body injury, also had a first-period goal.
Dallas' Mike Ribeiro received a double-minor for high-sticking with 49.5 seconds left in regulation after his stick struck Setoguchi in the face, giving the Sharks a power play that extended into overtime.
"I got my stick up," Ribeiro said. "It was a tough play."
All three of this season's meetings between the teams have gone beyond regulation, with Dallas winning the first two.
Joe Pavelski had two assists and Antero Niittymaki made 15 saves for the Sharks as the teams faced off for the second time in four days. Dallas took a 3-2 shootout victory at San Jose on Monday night, the last time the Stars played.
San Jose was coming off Wednesday night's 3-2 loss at Nashville. The Sharks wasted a 2-1 lead in the final 3 minutes of that one, allowing a pair of goals in a 44-second span.
"It was an important bounce-back," McLellan said. "They had two ways to go. They could have pouted and dragged themselves into the rink, but they played. Credit goes to the leadership group and the followers did what they were supposed to do."
Lehtonen stopped 39 shots for the Stars after missing the previous four games with lower back stiffness.
Niittymaki admitted he was a little rusty after sitting out seven of the past eight games.
Dallas took a 2-1 lead at 9:26 of the second period when Eriksson lifted the puck over Niittymaki from the right of the cage.
Mitchell tied it on the power play from the high slot 37 seconds later, and Setoguchi made it 3-2 at 11:49 when his wrist shot beat a screened Lehtonen.
Setoguchi has nine goals in 20 career games against Dallas.
"It's just one of those things. It could just be a confidence thing coming in," Setoguchi said. "For some reason, they go in. Maybe I'm just comfortable playing here, but it's all luck. It feels good to get a couple."
Wandell's goal with the help of a screen from teammate Steve Ott drew Dallas even at 3 at 7:56 of the third.
San Jose struck first on Setoguchi's rebound goal at 10:05 of the first period.
Morrow, wearing a full face shield after breaking his nose Monday night against San Jose, tied it at 1 from the right circle at 19:09, capitalizing on Dallas' first power play of the game.
Notes: The Stars are 7-0-3 in overtime this season. ... Before the game, Dallas activated forwards Krys Barch and Toby Petersen off injured reserve. Barch missed six games with a foot injury and Petersen sat out six games with a broken hand. ... Sharks D Kent Huskins was back after missing nine consecutive games with an upper-body injury. D Doug Murray (lower body) sat out his third straight game. ... Dallas' Marc Crawford coached his 1,100th NHL game. ... The Stars have killed off all four 5-on-3 situations of 1 minute or more this season.