Taye Taiwo could see his season brought to an abrupt end following an ill-advised singing session, with a possible suspension hanging over his head.
The Marseille full-back helped to toast the club's Coupe de la Ligue triumph over Montpellier on Saturday by joining fans in an anti-Paris St Germain chant.
Taiwo had scored the only goal of the game to take the trophy and was in excitable mood at the final whistle.
He grabbed a microphone at the end of the game and sang along with supporters as they taunted rivals PSG.
The French League [LFP] have taken a dim view of the Nigerian's actions and have confirmed that they are to investigate the incident before deciding what action, if any, to take.
A statement from the LFP read: "The LFP has decided to open an inquiry into the conduct of Taye Taiwo after the Coupe de la Ligue final between Marseille and Montpellier.
"The League will hand the file to the national ethics committee for possible further action."
Taiwo has apologised for his actions, telling OMTV: "I want to apologise for what I sang into the microphone at the Stade de France on Saturday night.
"Everyone has told me that it was wrong to have done that and it made them feel sick in the heart. Me too. Now I feel bad for having done that. I was euphoric. We had to win and we sang. I apologise again."
Meanwhile, Marseille have seen their title aspirations dealt a crushing blow with the news that Stephane Mbia is to sit out the remainder of the season.
The Cameroonian defender is expected to be missing until mid-May with a groin problem.
Coach Didier Deschamps said: "The news is not good. Mbia has a problem with his adductor muscle, he is not set to return until mid-May."
Mbia lasted just seven minutes of Marseille's cup final meeting with Montpellier before being forced from the field.