Bordeaux suffered their first defeat of the new Ligue 1 season at Guingamp on Sunday to lose top spot in the table to Lille, who beat Nantes earlier in the day.
First-half goals from Moustapha Diallo and Christophe Mandanne, the latter from a penalty, condemned Willy Sagnol's Bordeaux to a 2-1 defeat, with a late Cheick Diabate strike proving to be a mere consolation for the visitors in Brittany.
Lille had gone clear at the summit earlier in the day thanks to a 2-0 victory against Nantes in the far north, with Divock Origi scoring one goal and then setting up another for Portuguese youngster Rony Lopes.
Rene Girard's side, who will face the Russians of FC Krasnodar in the Europa League on Thursday, are a point ahead of both Bordeaux and Saint-Etienne, with champions Paris Saint-Germain a further point adrift in fourth.
Diallo headed home a free-kick from on-loan Newcastle United midfielder Sylvain Marveaux to put Guingamp ahead after 26 minutes, and Mandanne netted from the spot eight minutes later after Gregory Sertic had brought down Jeremy Pied inside the box.
French Cup holders Guingamp, who go to Fiorentina in the Europa League on Thursday, then held on after giant Malian Diabate had reduced the arrears in the 83rd minute, sweeping home first-time from a Thomas Toure cutback.
"In the first half the players' heads were not in it," admitted Bordeaux coach Sagnol, who had been widely praised after his team's fine start to the campaign.
"The return to action after the international break was difficult. I hope this will serve as a lesson for everyone that nothing will be easy this season, that if we want to achieve anything we will need to work, work and work all the time.
"Losing the status of leaders could be a good thing for us. It was maybe getting a bit difficult to deal with in recent weeks."
Lille continued their unbeaten start to the season as two goals in the first four minutes of the second period did for Nantes at the Stade Pierre-Mauroy.
After a goalless first half in which Jordan Veretout hit the post for the visitors, Origi opened the scoring within a minute of the restart, heading home a cross from Florent Balmont.
Three minutes later, the Belgian international, who was bought by Liverpool in the summer before being loaned back to LOSC, provided the pass for Lopes to apply the finish.
It was a first goal for the Portuguese midfielder since he moved to Lille on loan from Manchester City in the summer transfer window.
Marseille visit Evian in the day's late kick-off, while Saint-Etienne beat Caen 1-0 on Saturday as champions Paris drew 1-1 at Rennes, despite Zoumana Camara giving them a first-half lead.
Source: AFP