Monaco moved to the top of Ligue 1 on Saturday with a 3-0 win over last season's runners-up Lens who sunk into the relegation zone.
Ivory Coast striker Wilfried Singo headed in the opener for Monaco in the 23rd minute with Aleksandr Golovin stretching the lead 13 minutes later.
Guillermo Maripan added the third just before the hour mark as Monaco eased to a third victory in four matches this season.
Monaco have 10 points and are two points in front of Marseille who were held to a 1-1 draw by Nantes on Friday.
For Lens, it was their third defeat of the campaign and they are second from bottom.
It is a worrying start to the season for northerners Lens who were second last season, only missing out on the Ligue 1 title by a point to Paris Saint Germain.
They will also start their Champions League campaign in just under three weeks' time against Sevilla.
Franck Haise's team created very few chances on Saturday in a game where record 30-million-euro signing Elye Wahi struggled to make an impact.
Lens have now conceded 10 goals in four games; last season, it took 15 matches for them to give away a 10th goal.
In Saturday's early game, the Breton derby between Brest and Rennes ended in a 0-0 draw.
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