French rugby union player, Mathieu Bastareaud, is under investigation for making a homophobic comment during Sunday's European Champions Cup victory over Benetton.
The Toulon centre will face disciplinary action after the tournament organisers, European Professional Club Rugby, said they would look into the incident.
A ban would eliminate Bastareaud's chances of playing in the Six Nations, with France's opening match against Ireland on February 3.
Bastareaud has since apologised on social media, tweeting "I want to apologise for my reaction to the player's insults".
"I reacted badly in responding to his provocation, I'm sincerely saddened that I could have hurt people," he added.
Former England fly-half, Andy Gooded, condemned Bastareaud's comment.
He wrote on Twitter: "No place in the game for homophobia".
"Absolutely disgusting. I hope [EPCR] make an example of Bastareaud and ban him for a long time. Should throw the book at him."
European Professional Club Rugby said in a statement they were "made aware of the incident towards the end of the Rugby Champions Cup match".
It added: "The citing commissioner is considering the incident as part of his routine review of the match, and will make a decision when he has concluded his enquiries."
"It will be a duty of the referees to judge what Bastareaud said," they added.