Marseille paid the price for the second-half dismissal of Joey Barton as they slipped to a shock 1-0 defeat at home to lowly Nancy.
Barton was shown two yellow cards in the space of five minutes to leave OM facing an uphill struggle at the Stade Velodrome. And an own goal from Andre Ayew capped off a miserable evening for the title hopefuls, who remain six points behind Ligue 1 leaders Paris Saint-Germain.
It marked only the third win of the season for Nancy, lifting them off the foot of the standings and within four points of safety.
Ajaccio striker Adrian Mutu scored twice as Ajaccio inflicted a blow to Lyon's Ligue 1 title hopes by beating them 3-1.
Paris St Germain's three-point lead, gained by winning 4-0 in Toulouse on Friday, was sure to last the weekend after this surprising result.
Ajaccio were without a win in five league matches and perched precariously, just two points above the relegation zone, as Lyon arrived looking to rejoin PSG at the summit. And when Lyon edged ahead early in the second half it was all going to plan for Remi Garde's men.
But Ajaccio were soon level, thanks to Chahir Belghazouani, and Romanian Mutu headed them ahead before adding a late penalty after Lyon missed a chance to equalise from the spot.
Reims remain in the relegation zone after squandering a first-half lead in a 3-1 defeat at Montpellier.
Gaetan Courtet put the visitors in front on 33 minutes, but Montpellier equalised just three minutes into the second half through Souleymane Camara and went on to claim all three points thanks to goals from Marco Estrada and Younes Belhanda.