Lyon missed the chance to go top of Ligue 1 on Friday after sliding to their first defeat of the season, losing 2-1 at Lens.
Florian Sotoca scored the opening goal late in the first half at a rain-drenched Stade Bollaert and Matthieu Udol headed in a second for Lens on 76 minutes.
Udol was then sent off for a clumsy tackle on teenager Khalis Merah, who grabbed a consolation goal for Lyon.
Yannick Cahuzac won for the first time as Lens coach since replacing Dino Toppmoeller. The German was sacked last month after just six games in charge.
Lens ended a four-match winless run in the league to climb to seventh, a timely boost ahead of the visit of Sporting Lisbon in the Champions League on Tuesday.
Lyon remain two points behind leaders Monaco. Paulo Fonseca's side host last season's UEFA Conference League winners Crystal Palace in the Europa League on Thursday.
"Defensively we had problems because the team was too stretched and did not press the way we wanted. And when we had the ball, we lost it too quickly. We gave the first 45 minutes to Lens," Fonseca told reporters.
The Lyon coach also pointed to the limited preparation time available after the international break.
"I don't want to make excuses, but that's the reality. We had one day to prepare for the match. It's difficult to prepare a game like that. But I don't think it's an excuse," he said.