Sloan Privat and Nicolas Benezet gave Guingamp their first goals of the season in a 2-0 win which send Marseille crashing back to earth in Ligue 1`s only game on Friday.
Marseille had been riding a tide of euphoria since the arrival of new coach Michel with a 6-0 rout of Troyes last weekend following losses in their opening two games, but cold reality hit again in Brittany.
"The rhythm of the game was very fast and the opposition very strong," said Spaniard Michel, who took over after Argentine Marcelo Bielsa quit after the first game of the season.
"We lost a lot of individual duels not just defensive, but also for the possession and it was very difficult to take the ball. That`s something that we didn`t expect.
"The team did what they could but they are very young. We lacked assurance in our game."
The 26-year-old Privat had missed a penalty early on but made up by getting his team`s first goal after 72 minutes at the Roudourou Stadium with Benezet scoring the second with one minute to go.
Their first points of the season lift Guingamp off the bottom of the table just behind Marseille who are 13th, also with three points from four games.
It ended a series of eight consecutive defeats for Jocelyn Gourvennec`s Guingamp against Marseille.
"It`s difficult to host Marseille and to get your campaign back on track, but the team showed great determination and desire," said Gourvennec.
"To win 2-0 against Marseille is a great performance. We now have three points like Marseille."
Michel had started with the same lineup as against Troyes, but his side lacked the efficiency of the Velodrome a week ago.
Remy Cabella was the only bright spark as he organised midfield with Abdelaziz Barrada and Romain Alessandrini failing to feature, the latter missing a chance after 31 minutes following a Cabella cross.
Privat had missed a penalty for Guingamp after four minutes following a Lassana Diarra foul on Jimmy Briand with Steve Mandanda proving solid in the Marseille goal.
Marseille had largely dominated the first half but failed to break through the Guingamp defence.
Belgium forward Michy Batshuayi missed again just before the break when he pick up a Cabella cross only for his effort across goal skimming the post.
The Brittany side also missed chances with midfielder Moustapha Diallo heading right of goal on 25 minutes, and Marseille`s Benjamin Mendy cleared a Marcus Coco effort just before the break.
But Privat got the breakthrough when he picked up a Briand offering and turned into an empty net.
Marseille pushed for the equaliser in the final 15 minutes but came up against a tenacious Guingamp.
And it was the Bretons who got another when Benezet fired left to leave Mandanda with no chance.
In other Ligue 1 action this weekend, defending champions Paris Saint-Germain face their stiffest challenge of the early season away to Monaco on Sunday.
Laurent Blanc`s treble winners have yet to put a foot wrong on the way to a trio of victories that sees them two points clear of an unusual threesome of followers that includes Bastia, promoted Angers and former French champions Nantes.