"Jumbo really came to play," San Jose coach Todd McLellan said.
The Red Wings started strong and ended with a flurry of shots, but Antti Niemi denied them early and late with a 35-save performance to help the surging Sharks win their fourth straight and for the 13th time in 16 games.
"Our playoffs started 15 games ago," Thornton said.
The Central Division-leading Red Wings, who had won a season-high five straight, are trying to catch Vancouver for the top spot in the Western Conference and hold off teams such as San Jose for playoff positioning.
"We're not going to win every one, so this is nothing to get down about," said Jimmy Howard, who stopped 39 shots.
Henrik Zetterberg scored a power-play goal with 1:51 left to pull the Red Wings within a goal, but they couldn't beat Niemi again to force overtime.
"They made the plays in the end, give them credit," Detroit coach Mike Babcock said.
Ryane Clowe scored midway through the game on a breakaway he created by blocking a shot.
Detroit's Daniel Cleary scored game-tying goals early in the second and at the 14:42 mark of the period.
The Red Wings got off to a great start, outshooting the Sharks 9-1 midway through the first period and killing their 5-on-3 power play.
"If you're able to stop those, then it's easier the rest of the game," Niemi said.
Thornton scored the game's first goal on a power play with 18 seconds left in the period, becoming the 18th active player with 300 goals.
"It's nice," he said. "I didn't know until Patty [Marleau] told me."
"He's very good with the puck and he uses his size to his advantage," Detroit defenseman Nicklas Lidstrom said. "He's hard to defend with or without the puck."
Cleary tied the game at the 7:06 mark of the second period and knotted it up again -- 34 seconds after Clowe's goal -- late in the second, giving him a career-high 21 goals.
Setoguchi put the Sharks ahead for good with 1:17 left in the second period and made it a two-goal lead at 13:12 of the third.
The Sharks needed that cushion.
Niemi made several tough saves in the final period -- including some against streaking Pavel Datsyuk -- to make it difficult for the Red Wings to come back, but Zetterberg took advantage of Dany Heatley getting called for interference late in the game.
In the final minute, Niemi made key saves on shots by Lidstrom and Johan Franzen to deny Detroit a comeback.
"Nemo, that's just another night for him," McLellan said. "The save at the end against Franzen was a big one."
Red Wings F Patrick Eaves left in the second period, appearing to hurt his right knee when he led with it on a check against Torrey Mitchell. Babcock wasn't able to update his status after the game. ... Thornton snapped a nine-game skid without a goal. ... Detroit G Chris Osgood (hernia surgery) said he's feeling "much better" after several practices and might be able to play March 11 at home against Edmonton or the next day at St. Louis. ... San Jose's Logan Couture needed stitches after his chin was cut by Detroit's Jonathan Ericsson, who was called for high-sticking. McLellan said the rookie was cut again a couple of minutes later when Lidstrom was called for high-sticking. ... The Red Wings hope Valtteri Filppula (left knee) will be able to return soon. ... Modano told NHL.com on Tuesday that he plans to return Saturday against Buffalo.
Information from The Associated Press contributed to this report.
Arena: Joe Louis Arena Location: Detroit, Michigan
Referees: Bill McCreary, Chris Rooney Linesmen: Steve Barton, Scott Driscoll
Attendance: 20,066 (100.0% full)
Team Stat Comparison
Power Play Goals
Power Play Opportunities
Shots on Goal
Joe Thornton (15)
(Power Play) Assists: Joe Pavelski, Dan Boyle
Daniel Cleary (20)
Assists: Jiri Hudler, Nicklas Lidstrom
Ryane Clowe (17)
Daniel Cleary (21)
Assists: Jiri Hudler, Niklas Kronwall
Devin Setoguchi (16)
Assists: Joe Thornton, Logan Couture
Devin Setoguchi (17)
Assists: Joe Thornton, Logan Couture
Henrik Zetterberg (18)
(Power Play) Assists: Tomas Holmstrom, Johan Franzen
Devin Setoguchi has been scoring at will in his last 2 games after not finding the back of the net very often during the first 50 games this season. Setoguchi followed up his first career Hat Trick on Saturday with 2 more goals Tuesday.