Monaco missed the chance to climb back up to second place in Ligue 1 when they lost 2-1 at home to Toulouse on Sunday while Rennes comfortably beat Clermont 3-1 to continue their winning streak.
Toulouse opened the scoring in the 41st minute when skipper Vincent Sierro caught Monaco goalkeeper Philipp Kohn out of position on a free-kick.
Monaco levelled just after the restart through Maghnes Akliouche but failed throughout the game to capitalise on a host of other chances.
Centre-forward Folarin Balogun was the main culprit. The American fluffed an early one-on-one with goalkeeper Guillaume Restes and then squandered another golden opportunity from close range after being set up by Thilo Kehrer.
Toulouse made them pay in the 70th minute when a corner fell for defender Logan Costa to fire in.
Defeat means Monaco stay fourth on 38 points, level with Lille, who beat Le Havre 3-0 on Saturday, and one point behind Nice who slipped to a 1-0 loss at Lyon on Friday.
Paris Saint-Germain, who beat Nantes 2-0 on Saturday, remain clear leaders on 53 points, 14 ahead of Nice.
Brest, 37 points, can take over second spot if they beat Marseille in Sunday's late game.
Rennes, meanwhile, made it six wins on the bounce with a 3-1 victory over bottom-placed Clermont, thanks to a brace from in-form midfielder Martin Terrier and one from Warmed Omari.
It would have been more had Clermont goalie Mory Diaw not kept out Ludovic Blas's 38th minute penalty.
Rennes are seventh with 34 points, in touching distance of the European places.
Clermont, however, remain rooted to the bottom with just 16 points, one fewer than Metz who lost 3-0 at Montpellier.
Lorient climbed out of the bottom three with a 3-1 win over Strasbourg with new signing Mohamed Bamba scoring twice.
