Montpellier ended Marseille's resurgence with a 1-0 win in Ligue 1 on Saturday, while eight-man Nice went down 2-0 at home to St Etienne.
Slowly recovering from a difficult start to the season, Marseille had managed three league victories in succession coming into the clash at the Stade de la Mosson.
But they proved to be the architects of their downfall against Montpellier, with a 61st-minute own-goal from Souleymane Diawara gifting the hosts a 1-0 win.
This season's surprise package, Montpellier have now recorded four wins in their last five league matches.
They occupy second place in the standings, level on points with leaders Paris Saint-Germain, who host Nancy on Sunday.
Elsewhere, Rene Marsiglia endured a nightmare start to his reign as Nice coach.
Handed the top job after Eric Roy was moved into a general manager role this week, Marsiglia could only watch as his team found themselves down to nine men within the first 30 minutes of their match at home to St Etienne.
Goalkeeper David Ospina was the first to go after bringing down Pierre-Emerick Aubameyang in the 23rd minute.
Florent Sinama-Pongolle scored from the spot to make it 1-0.
Just four minutes later Eric Mouloungui followed his goalkeeper in making an early exit when he saw red for a bad tackle on Fabian Lemoine.
St Etienne were cruising when Kurt Zouma's header made it 2-0 eight minutes before half-time.
And Nice finished the match with just eight players after Renato Civelli received his marching orders for a dangerous challenge on goal-scorer Sinama-Pongolle.
In other matches, Yannick Sagbo's penalty and a Daniel Wass goal helped newcomers Evian defeat Lorient 2-1 at home.
On a good day for the promoted teams, Dijon ran out 2-0 winners in their match at home to Bordeaux, with Brice Jovial and Benjamin Corgnet the men on target.
Even struggling Ajaccio picked up a point.
The Corsican club are bottom of the table after losing their last four league matches.
But they salvaged a 2-2 draw at home to Caen thanks to Benjamin Andre's 91st-minute equaliser.