Frenchman Bardet, runner-up last year, had his AG2R-La Mondiale team pile on the pressure in the descent from the Col de la Biche, one of three out-of-category climbs, which led Chris Froome's (Team Sky) lieutenant Geraint Thomas to crash and break his right collarbone.
AG2R-La Mondiale, who are based in the Chambery area where the stage was held, used their knowledge of the terrain to blow the race wide open.
Bardet, known for his aggressive style, went on the attack on the last descent, distancing race leader Froome and other rivals.
He was only caught two kilometres from the finish after a bold solo ride in the final flat part of the stage won by Colombian Rigoberto Uran (Cannondale-Drapac).
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"I loved it, they took risks, AG2R were really aggressive," LeMond said.
"I love seeing a team strategy that's really ripping things apart. It's part of the strategy to string things out.
"What Bardet did was grand style."
Bardet sits third overall, 51 seconds behind Froome and 33 seconds adrift of Italian Fabio Aru (Astana).
"There will be other battles to fight in the Pyrenees and in the Alps," the Frenchman warned.
LeMond believes that although Froome remains the overwhelming favourite to add to his 2013, 2015 and 2016 titles, three riders are still in the mix to unsettle the Briton.
"The real players are Froome, Aru, Bardet and Uran, who is going to do better than people think. He's the dark horse," said the American, who won the Tour in 1986, 1989 and 1990.
Uran is fourth overall, 55 seconds off the pace, and his Cannondale-Drapac team manager Jonathan Vaughters refers to him as "Voldemort, the guy whose name can't be mentioned."
“I don’t know if I can win it [the Tour], but every which-way I’m going to fight to do so. “I’ll continue to be very attack-minded. “I’ve noticed that there are four or five climbers who are practically at the same level. Between us it will be a battle that is as psychological as it is tactical, and also about the ability of each person to absorb tough stages and a fast pace.” - Romain Bardet
The Tour resumes tonight with a flat tenth stage between Perigueux and Bergerac before the big guns battle it out again in the Pyrenees on Thursday.
