Marseille suffered a second successive defeat and saw their Ligue 1 titles hopes suffer a blow when they lost 2-1 at Montpellier on Friday.
A week after losing to fourth-tier Grenoble in the French Cup, the former European giants were sunk at the Stade de la Mosson which was hosting a game for the first time since floods in September swamped the arena.
Marcelo Bielsa's Marseille still lead Ligue 1 but they can be deposed by Lyon if they defeat Toulouse on Sunday.
Friday's result also allowed Montpellier to clinch the league double over their heavyweight rivals having won 2-0 at the Stade Velodrome earlier in the season.
Kevin Berigaud and Paul Lasne scored for Montpellier either side of the interval with Bilel Omrani giving Marseille hope with a goal just two minutes after coming on as a substitute.
"Losing is always a concern and this defeat affects us," said Bielsa.
"But being top is not a pressure, it's a challenge. That's how it should be."
Montpellier coach Rolland Courbis said he was delighted with the three points but still backed Marseille to be amongst the title favourites.
"We are happy to have taken six points off Marseille this season, but I also savour every one of our 29 points," he said.
"Marseille have just five defeats in 20 matches -- they and Lyon will be the champion favourites. PSG have a tough schedule."
The game got off to an emotional start with a minute's silence observed in memory of the victims of this week's Paris massacres followed by a rousing rendition of La Marseillaise.
Both sets of players sported "Je Suis Charlie" T-shirts during the warm-up and wore black armbands.
Berigaud gave Montpellier a deserved 36th-minute lead in controversial circumstances with a superb piece of control with his left foot before firing a right-foot drive from the edge of the box past Steve Mandanda in the Marseille goal.
But Marseille believed play should have been halted for a foul on Brice Dja Djedje who lost possession in the build-up to the goal.
Lasne, who had created his team's opener, then made it 2-0 after 62 minutes after a muscular charge by Anthony Mounier took out two defenders.
His pass found an unmarked Lasne who scored confidently from the edge of the six-yard box.
Omrani gave Marseille hope by cutting the deficit six minutes later but it was Montpellier who finished the stronger.
Marseille have now gone seven away games without a win in all competitions and looked weakened on Friday with Africa Cup of Nations-bound Andre Ayew and Nicolas Nkoulou both absent.
Source: AFP