Rayan Cherki fired Lyon to a 2-1 Ligue 1 win over Lens at the Groupama Stadium on Sunday as the visitors' slump in form saw them drop out of the top three.
Lens, who have exceeded expectations since returning to France's top flight in 2020, missed the chance to draw level on points with second-placed Marseille and have picked up just two points from their last four league matches.
The result left Monaco – who beat leaders Paris Saint-Germain on Saturday – in third and Lens in fourth, while Lyon remain six points off the European spots in ninth.
Angry Lyon supporters protested outside the stadium before kick-off against the club hierarchy, blaming them for the decline of one of French football's traditional heavyweights.
Former Arsenal star Alexandre Lacazette put the hosts in front against the run of play in the 23rd minute as he collected Cherki's pass and drilled his shot into the bottom corner.
The France striker's 14th league goal of the season did not dishearten Lens, who equalised in the 39th minute when Deiver Machado's rocket into the top corner finished off a flowing move.
Midfielder Cherki, 19, scored the winner in the 64th minute with a precise finish in the area after good work by Maxence Caqueret.