Marseille's stunning start to the Ligue 1 season which saw them win six from six games came to a spectacular end on Sunday as mid-table Valenciennes whipped them 4-1.
A double by much-travelled striker Anthony Le Taellec and one apiece from Foued Kadir - gifted to him by Marseille goalkeeper Steve Mandanda - and a brilliant opener by Gael Danic gave Valenciennes the points with Jordan Ayew scoring a consolation in time added-on.
Marseille - who were going down to their first defeat in all competitions this season as they had drawn three and won two of their Europa League games - still top the table leading PSG by three points, although Lyon can pull to within one if they beat Bordeaux at home later on Sunday.
Marseille - who had only conceded one goal in all Ligue 1 games this season prior to the game - went behind in the 16th minute with a superb freekick by Danic although Mandanda let rip at his wall, which he felt should have jumped higher.
Le Taellec, who numbers unsuccessful spells at both Liverpool and Sunderland among his many clubs, doubled the lead in the 35th minute putting away a super cross by Danic.
Any hope Marseille had of regrouping at the break disappeared when Mandanda completely fluffed a throw out from inside his area which landed at Kadir's feet just outside the box and he put it away with the Marseille goalkeeper vainly trying to regain his goal.
Le Taellec added his second in the 65th minute with a header from another Danic cross to send the record attendance of just over 22,000 wild and give Marseille plenty to think about ahead of their home game with bitter rivals PSG next Sunday.
For Valenciennes it maintained their hold over Marseille, who have beaten them just once since the former were promoted in 2006.
On Saturday, Paris Saint-Germain had geared up for a testing week with a comfortable 2-0 win at home to Sochaux.
Kevin Gameiro's first-half brace at Parc des Princes gave PSG their fifth consecutive win in all competitions, ahead of Wednesday's visit to Porto in the Champions League and next weekend's trip to Marseille.
"It was a good victory, a good match, particularly in the first half, when we played with more intensity," said PSG coach Carlo Ancelotti.
"In the second half we were too conservative and the rhythm was too slow. We needed more rhythm. Perhaps some of them were thinking about the next matches. It's not right, but maybe that was it."