Lyon suffered a shock first defeat of the season in any competition as Jacques Faty and Sloan Privat gave Sochaux victory.
Coach Francois Gillot had spoken before the game of his desire to obtain a shock result for team-mate Charlie Davies, who was hospitalised after suffering career-threatening injuries in a car crash which left a female passenger dead.
And they did so despite a second half of almost relentless pressure from the hosts, for whom the result is the worst possible preparation for Tuesday's Champions League clash with Liverpool.
Lyon were first to threaten as Lisandro Lopez's shot was parried by goalkeeper Teddy Richert, the loose ball rebounding off defender Faty and inches wide of the post.
But they fell behind in the 16th minute as keeper Hugo Lloris was impeded by team-mate Jeremie Toulalan while trying to claim a corner and Faty seized on the confusion to stab the ball home from close range.
Bafetimbi Gomis twice went close to an equaliser within three minutes as his shot was blocked and his follow-up effort skimmed the left-hand post on its way wide.
And, after Sochaux's Vincent Nogueira had gone close from long range, Lisandro had another opportunity for the hosts but shot narrowly wide of the right-hand post.
That set the tone for Lyon's dominance after the interval, with Miralem Pjanic volleying narrowly off target from Gomis' cross before Richert denied Ederson.
Gomis then narrowly failed to reach Yannis Tafer's cross-cum-shot and Toulalan played in Michel Bastos to hit the crossbar as the home side went closer and closer to a leveller.
But a breakaway move led by Yassine Mikari two minutes from time allowed Privat to beat Lloris and make the game safe.
