Tobias Enstrom scored a power-play goal with 3:36 remaining in the third period to help the Winnipeg Jets deal a blow to San Jose's chances to finish in first place by beating the Sharks 4-3 on Thursday night.
"We've let some teams that are not as good in the standings beat us and take points away, for whatever reason I'm not sure," captain Joe Thornton said.
The Sharks have lost six games since the Olympic break, all to teams that would not be in the playoffs if the season ended now. San Jose still holds a two-point lead over Anaheim in the Pacific Division but the Ducks have three games in hand.
"We can't give away points," forward Joe Pavelski said. "We've given away a few too many lately. They got the games in hand. If they do their job they'll be there but there's still quite a bit of hockey left."
Blake Wheeler added a goal and two assists for the Jets, who trail Phoenix by nine points in the race for the second wild card spot in the Western Conference. Andrew Ladd and Dustin Byfuglien also scored, and Al Montoya made 27 saves.
"We talked about the playoff race for the first time tonight," Jets coach Paul Maurice said. "It's a long hill to climb but this is the way we need to play every night."
Couture scored the tying goal in the second period for San Jose but then committed the penalty that led to the game-winner when he shot the puck over the glass while trying to kill a penalty.
The Sharks managed to kill 11 seconds of the 5-on-3 but couldn't kill the second penalty when Wheeler slid a pass to a pinching Enstrom, who beat Niemi.
"We're a long shot coming into the building against arguably the best team in the league," Wheeler said. "We just tried to make one more play than they did and it worked out for us."
The Jets took a 3-2 lead by scoring twice in the first 10 minutes of the second period. The equalizer came early when Wheeler skated into the offensive zone and fired a bad-angle shot at Niemi from along the goal line that somehow sneaked into the net.
Winnipeg took its first lead after Thornton negated a San Jose power play with a tripping penalty. Just seconds after Paul Postma came out of the box to give the Jets a power play, Wheeler slid a perfect pass to Byfuglien, who beat Niemi with a one-timer for his 20th goal.
"Our power play was kind of sloppy but we were able to pull together a couple of times and set it up," Ladd said. "I wanted to come here, have a good effort and give ourselves a chance to win, and we did that."
The Sharks tied it later in the second when they capitalized on another power-play chance. James Sheppard's slap shot deflected off Couture's thumb and into the net to give San Jose its fifth power-play goal in two games. Couture also got his 20th goal in his return to the lineup after missing one game with an injury from blocking a shot on Monday in Calgary.
The Sharks opened the scoring less than 2 minutes into the game when Sheppard sent a pass from the point that deflected off Marty Havlat's stick and right to Boyle, who beat Montoya with a backhand for his first goal in 30 games.
The Jets answered just 36 seconds later when Ladd put in a rebound of Michael Frolik's shot for his 22nd goal. It came in Ladd's first game back after missing Monday's tilt in Dallas for the birth of his daughter.
"There's a little bit of energy in the building, and bang it's gone," Sharks coach Todd McLellan said. "They come right back down and score and we have to start all over. That was probably a bit of a turning point, may have been an indication of things to come."
San Jose went back in front late in the period on Burns' power-play goal.
Thornton became the 100th player to play in 1,200 career NHL games. ... Former Sharks F Devin Setoguchi was a healthy scratch for the Jets. ... San Jose recalled F Freddie Hamilton from Worcester of the AHL to replace F Adam Burish, who had surgery on two broken fingers on his left hand.