Mario Balotelli was sent off for the third time this season in Ligue 1 as Nice leapfrogged Paris Saint-Germain into second place in the table after a 1-0 win at bottom club Lorient.
Balotelli, a free signing from Liverpool last summer, was shown a straight red card for dissent in the 68th minute.
From initial video replays, it seemed difficult to ascertain what Balotelli did wrong other than backing into Lorient defender Zargo Toure with his arms up as they challenged for a ball.
Nice coach Lucien Favre was no closer to an explanation after the game, although he suggested Balotelli may have spoken out of turn to referee Tony Chapron.
"I didn't see what happened. All of a sudden he was coming off and I said to myself, 'What's happened?'" Favre said. "I didn't see when he gave the red card and I don't know why. It seems that he talked back to the referee."
Favre refuted any notion that Balotelli might be getting singled out unfairly by referees, adding: "He's not on referees' radars. They are totally neutral. If there is reason to send a player off, then they will.''
Balotelli, who has scored 11 goals for Nice this season, was dismissed for two yellow cards against Lorient in October and received a straight red card in the goalless draw at Bordeaux in December.
Nice had taken a 15th-minute lead through Wylan Cyprien's low angled shot and although Lorient went close to equalising on several occasions, through Majeed Waris and Alhassan Wakaso in particular, the visitors held on for their first away win since November.
Earlier, Marseille beat Rennes 2-0 at home to stay sixth, but they moved level on points with St Etienne.
Clinton N'Jie marked his return to the side following African Nations Cup duty with Cameroon by breaking the deadlock just before the hour mark and Newcastle midfielder Florian Thauvin, in his second season on loan with Marseille, added the second five minutes later.
Rennes, who had drawn their previous five league games, are without a win in their last 10.
Jonathan Bamba's early goal was enough to secure Angers a 1-0 home win against Nancy.
Forward Bamba fired Cheikh Ndoye's knockdown into the bottom corner in the fifth minute and Angers held on to make it back-to-back league wins.
Metz salvaged a point from a 1-1 home draw against Nantes courtesy of Cheick Diabate's stoppage-time penalty.
Nantes substitute Oswaldo Vizcarrondo was penalised for his challenge on Simon Falette and Diabate converted his spot kick into the bottom corner in the first minute of added time.
Valentin Rongier's 68th-minute strike had appeared to have been enough to clinch Nantes victory.
Lille gave their survival hopes a big boost by winning 2-0 at relegation rivals Caen despite the second-half dismissal of Adama Soumaoro.
Eric Bautheac and Anwar El Ghazi scored for Lille within 10 minutes of each other midway through the second half as Caen went down to a third straight league defeat.
Defender Soumaoro was shown a straight red card for his foul on Yassine Benzia in the 63rd minute.
Information from The Associated Press was used in this report.