Monaco keeps up pressure on PSG
James Rodriguez curled in a free kick in the 19th minute to give Monaco the lead after the Colombia forward was tripped by Cheikh M'Bengue.
Anthony Martial was handed his first league start in place of the injured Falcao and the 17-year-old forward scored on the stroke of halftime, exchanging passes with Emmanuel Riviere just inside the area before firing into the bottom right corner.
Rennes almost got one back 12 minutes from time but Tiemoue Bakayoko's effort crashed off the right upright.
Monaco remained a point behind Lille but is provisionally two points behind defending champion PSG, which hosts Lyon on Sunday.
Halftime substitute Ronny Rodelin scored the only goal of the game, two minutes after going onto the field. Pape Souare crossed to the far post where Rodelin was waiting to send a strike into the bottom left corner with his first touch.
Lille was forced to play almost the entire second half with 10 men after Franck Beria was sent off following a second booking in the 53rd but goalkeeper Vincent Enyeama managed to keep a 10th successive clean sheet, stretching the time he has not conceded a goal to 945 minutes, The Nigerian is just short of PSG goalkeeper Salvatore Sirigu's second-best mark of 948 from last season.
Valenciennes remained rooted in the bottom three.
Lorient won 3-0 to hand Nice its fifth defeat in a row.
Kevin Monnet-Paquet opened the scoring in the 17th minute and Vincent Aboubakar almost doubled Lorient's lead two minutes later but his header crashed off the post.
Nice defender Jordan Amavi turned the ball into his own net in the 71st and Aboubakar sealed the result in stoppage time.
Toulouse ended a run of four matches without a win as Wissam Ben Yedder scored a hat trick to help his team to a convincing 5-1 victory over bottom club Sochaux.
Sochaux goalkeeper Simon Pouplin and defender Lionel Zouma both scored own goals.
Cedric Bakambu had a goal harshly ruled out for offside for the visitors.
Elsewhere, Guingamp beat Nantes 1-0 thanks to a 63rd-minute header from Younousse Sankhare.
Saint-Etienne eased to a comfortable 4-0 win at home to Reims.
After a goalless first half in which both teams struggled to get shots on target, Bayal Sall broke the deadlock shortly after the hour mark, heading home Romain Hamouma's corner.
Saint-Etienne doubled its lead in the 76th minute when Loic Perrin headed in Yohan Mollo's free kick, and the captain added a second two minutes later. Reims goalkeeper Kossi Agassa managed to parry Sall's header but Perrin headed in the rebound.
Mevlut Erding added a fourth three minutes from time as Saint-Etienne moved provisionally fifth.