A second-half goal from Brandao gave Marseille a 1-0 victory over a lacklustre Chelsea at the Stade Velodrome.
Brandao pounced nine minutes from time when a cross from Taye Taiwo was deflected into his path by Ramires and the Marseille striker tucked the ball home from six yards. It was Chelsea's first defeat in Europe this season and the English champions looked well below par as their poor run continues.
Marseille's Mathieu Valbuena rattled the crossbar with a 20-yard drive that had Petr Cech well-beaten in the early stages.
And in the 15th minute there was total confusion when Chelsea appeared to have been awarded a penalty by Russian referee Vladislav Bezborodov after Souleymane Diawara brought down Florent Malouda. The Russian pointed to the spot but, under pressure from Marseille players, consulted his linesman and changed his mind.
Marseille had a goal ruled out for offside in the 35th minute when Gabriel Heinze was adjudged to have got ahead of the Chelsea defence from Benoit Cheyrou's free-kick. Heinze rose unchallenged to head home from six yards but was immediately flagged offside by the referee's assistant.
Goalmouth incidents were rare in the second half, with Brandao eventually winning it for the home side.