Paris: Monaco`s recent charge up the Ligue 1 standings came to a shuddering halt on Sunday when they conceded a first goal in over 800 minutes to fall 1-0 at ten-man Guingamp.
The result leaves Monaco fifth on 40 points while Saint Etienne, who drew 3-3 with Lens on Friday, have 41 in fourth, but only the top three in France qualify for the Champions League.
Croatian international `keeper Daniel Subasic had not let in a league goal for Monaco in 842 minutes when Dorian Leveque tapped in at the far post for Guingamp after Claudio Beavue beat the backline with a searching pass in the 52nd minute.
And this came despite the numerical advantage enjoyed by the visitors after Guingamp midfielder Moustapha Diallo was red-carded on 21 minutes for a studs up challenge.
Monaco lost a League Cup semi-final to Bastia in midweek after a penalty shoot-out and had been unbeaten in the league since November.
They were runners-up in Ligue 1 last season and are looking forward to facing Arsenal in a Champions League last-16 two-legged affair.
Monaco were on an eight match unbeaten run in the league, with five straight wins on the road, while Guingamp extended their winning streak at home to six straight wins.
France`s top three teams went into the weekend separated by two points with leaders Lyon on 49 hosting Paris Saint Germain, on 47 and who can go top if they win in Sunday`s much awaited late match.
Marseille also went into the weekend on 47 but drew 1-1 at Rennes to pull within one point of Lyon.
Swedish striker Ola Toivonen gave Rennes the lead after 26 minutes, smartly chesting down a loose ball to score past Steve Mandanda in the Marseille goal.
Marseille were saved when Lucas Ocampos, the Argentine signed on loan from Monaco in the last moments of the transfer window, found the net in the 59th minute after coming on as a half-time substitute.