Colombia midfielder James Rodriguez scored with a low curling shot from the edge of the box in the 18th minute and leftback Andrea Raggi doubled the lead by heading home a corner in the 72nd. Rodriguez made it 3-0 with a penalty in the 76th before Nantes midfielder Alejandro Bedoya scored a consolation goal in the 78th.
“Monaco must suffer and fight since the start of the season to get results,” Monaco coach Claudio Ranieri said. “We have a six-point lead, that’s good, but we must keep going because the next games will be tough.”
Monaco trails leader Paris Saint-Germain by 13 points with just six rounds left.
Saint-Etienne lost ground in the race for a Champions League spot by drawing at home with mid-table Nice 1-1, while Lyon kept its hopes for a European spot alive by edging relegation-threatened Valenciennes 2-1.
Monaco broke the deadlock when Dimitar Berbatov set up Rodriguez, who managed to curl a shot despite three defenders surrounding him. TV replays showed the goal should have been disallowed because Berbatov was in an offside position.
Nantes then created chances but lacked the finishing touch to level.
Monaco added a second goal just when Nantes enjoyed a good spell of domination as Raggi outjumped Lucas Deaux to head into the bottom corner. Four minutes later, Rodriguez scored from the penalty spot after Nantes goalkeeper Maxime Dupe brought down Fabinho.
Nantes was finally rewarded for its efforts when Bedoya headed a cross from Johan Audel into the top corner.
At Saint-Etienne, substitute Max-Alain Gradel salvaged a point for the hosts by converting a penalty in the last minute after Nice midfielder Didier Digard was red-carded for blocking a goal attempt from Josuha Guilavogui with his hand. Mathieu Bodmer nodded home a corner to initially put Nice ahead in the 58th minute.
“Freshness is an essential factor at the end of the season and we lacked freshness this afternoon,” Saint-Etienne coach Christophe Galtier said. “My players did not feel good. Our game was poor even though Nice did not have many opportunities.”
Saint-Etienne trails third-place Lille by five points.
Lyon striker Bafetimbi Gomis notched his 100th career goal in the league by opening the scoring with a low effort in the 30th but Valenciennes striker Majeed Waris equalized in the 66th. Jordan Ferri restored Lyon’s lead with a powerful long-range strike in the 69th.
Valenciennes was down to 10 men in the 84th when Marco Da Silva was red-carded for clattering into Lyon forward Alexandre Lacazette.
Lyon goalkeeper Anthony Lopes preserved the win by stopping a penalty from Waris in the 86th after Maor Melikson’s cross hit Ferri’s arm.