Metz passed up the chance to collect some much-needed points as they held Caen to a goalless draw on Saturday night.
PSG went top of Ligue 1 for the first time this season after title-rivals Lyon lost 2-1 at home to 10-man Nice on Saturday.
Ivory Coast winger Max-Alain Gradel scored for the fourth straight match as Saint-Etienne secured a 3-2 win at struggling Metz.
St Etienne closed back to within a point of fourth-placed Monaco as they eased to a 3-2 win away to rock-bottom Metz.
Paul-Georges Ntep's first-half strike was enough to give Rennes back-to-back wins with a 1-0 triumph over Ligue 1's bottom side Metz.
Basement-dwellers beaten in relegation six-pointer as Evian climb out of bottom three
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