Lille were left hanging on to a UEFA Champions League place by a single point following their 1-0 defeat at Nice on Sunday.
Later, former multiple champions Lyon fell 2-0 at Rennes and Marseille were held 2-2 by Toulouse at the Velodrome.
Saint-Etienne's 3-0 success over struggling Valenciennes on Saturday had put the pressure on Lille but the 2011 champions failed to respond.
Former Paris Saint-Germain forward Mathieu Bodmer scored the only goal with a cute back-heel in first half stoppage time, although there was a suspicion of offside.
At the turn of the year, Lille were challenging the top two, PSG and Monaco, but they have now dropped to 13 points off the summit after earning just two points from their last five matches.
Marseille remained in fifth, on 36 points, after their stalemate at home.
Toulouse striker Wissam Ben Yadder levelled on 11 minutes with Serge Aurier ensuring they went home with a point on the hour.
Lyon, who pitched up seeking a fourth straight league win, had a torrid time of it at Rennes.
They went down a man when Samuel Umtiti was red carded for an ill-judged tackle on Romain Alessandrini three minutes from the interval.
Rennes were already leading at that stage thanks to Cedric Hountondji's 22nd minute header and new signing, Swedish forward Ola Toivonen, doubled up with less than half an hour left.