In-form Alexandre Lacazette scored before coming off injured in the first half as Lyon collapsed to a 4-2 defeat away at promoted Dijon in Ligue 1 on Saturday.
Lacazette put the visitors 2-1 up on 37 minutes at the Stade Gaston-Gerard with his sixth goal already this season after Corentin Tolisso’s opener for Lyon had been cancelled out by a Frederic Sammaritano penalty.
But the 25-year-old, who on Thursday was recalled to the France squad for the start of their World Cup qualifying campaign, then hobbled off just before the break and was later seen with strapping and an ice pack around his left knee.
Things got worse for Lyon as Dijon came roaring back with goals by Julio Tavares, Dylan Bahamboula and Pierre Lees-Melou to claim their first points since returning to the top flight.
“I am worried. When a player comes off before half-time it is always worrying,” Lyon coach Bruno Genesio told Canal Plus at half-time before adding that the player would undergo tests today to determine the extent of the problem.
Lyon do not play again until hosting Bordeaux in a fortnight but Lacazette must now be a major doubt for France’s upcoming matches in Italy and Belarus.
The situation is similar for Nabil Fekir, who was recalled to the national set-up for the first time since suffering a serious knee injury in France’s friendly win in Portugal alost a year ago.
But he came off in the second half and Lyon president Jean-Michel Aulas later revealed he may undergo minor knee surgery on Monday.
“We flouted the fundamental principles of football and were deservedly beaten. Losing Lacazette hurt us and we did not play as well in the second half,” said Genesio of the defeat.
Guingamp are the provisional leaders of the fledgling table after a 2-0 win at promoted Nancy, although they are level on points with Nice, who drew 1-1 at home to Lille.
Vincent Koziello put Nice ahead at the Allianz Riviera only for Lille captain Franck Beria to equalise with his first goal in Ligue 1 since November 2010.
Caen beat Bastia 2-0, Metz defeated Angers by the same score and Rennes came from behind to draw 1-1 at Montpellier.
Marseille recorded their first win of the season on Friday, beating Lorient 2-0 at the Stade Velodrome.