Paris St Germain extended their lead at the top of Ligue 1 to 11 points after a narrow 1-0 win at 10-man Nantes - which ended in controversy after referee Tony Chapron lashed out at Diego Carlos.
The official aimed a kick at Nantes defender Carlos before dismissing him after the pair collided in injury time.
Angel Di Maria's early goal set Unai Emery's side on their way to victory at the Stade de la Beaujoire on Sunday.
It was PSG's seventh straight win in all competitions as they moved 20 points ahead of fifth placed Nantes.
Claudio Ranieri's Nantes improved after the break and were denied a leveller when Emiliano Sala's header was disallowed for offside.
PSG were without the injured Neymar but made light work of their hosts in the first half and Di Maria won it after 12 minutes when he drilled into the bottom corner.
The former Manchester United winger also missed a golden chance eight minutes before the break when he somehow hit the bar from six yards.
The visitors should have killed the game off in the first half but Nantes upped the tempo after the break and Carlos glanced a header wide three minutes after the re-start.
Di Maria missed another fine chance when he fired wide after 56 minutes and PSG were almost made to pay five minutes later.
Leo Dubois' free kick was nodded in by Sala but Abdoulaye Toure, who had also attacked the ball, was offside and the goal was ruled out.
Nantes put PSG under huge pressure but could not force a deserved leveller and the evening ended in bizarre and controversial circumstances.
Costa was racing back to try to stop a PSG break and accidentally collided with referee Chapron, who then kicked out at the defender while on the ground.
Costa was dismissed for a second yellow card, apparently for dissent, and PSG almost added a second when Adrien Rabiot hit the post.