Paris St-Germain’s Idrissa Gueye refused to play in a match to avoid wearing a rainbow symbol in support of LGBTQ+ rights.
The 32-year-old former Aston Villa and Everton midfielder was absent from Saturday’s 4-0 win over Montpellier.
PSG boss Mauricio Pochettino said only that Gueye missed the game for “personal reasons”.
The French Football Federation (FFF) has reportedly written to Gueye to clarify why he was absent.
BBC Sport has approached Gueye’s representatives for comment.
Crystal Palace’s Cheikhou Kouyate and Watford’s Ismaila Sarr have posted on social media in apparent support of their Senegal team-mate’s stance.
Kouyate posted a picture of himself alongside Gueye on Instagram, with a caption calling Gueye “a real man”. Watford winger Sarr posted a picture of him and Gueye accompanied by three heart emojis and the caption “100%”.
In response to Sarr’s post, Watford reiterated their commitment to equality and diversity, adding “this includes the willingness to offer further education and support to any of its employees”.
At a news conference on Wednesday, Crystal Palace boss Patrick Vieira said if his player had posted in relation to Gueye, he would speak to them. “It’s going to be an in-house conversation,” he added.
Homosexuality is illegal in Senegal and punishable by prison sentences of up to five years.
For the second successive season, clubs in France have been invited to mark 17 May’s International Day Against Homophobia, Biphobia and Transphobia by wearing rainbow-design numbers on the back of their shirts.
In addition to missing Saturday’s win over Montpellier, Gueye, who arrived at PSG for £30m in July 2019, missed last year’s show of solidarity citing gastroenteritis, according to Le Parisien newspaper, who first reported the reason for his absence.
The AFP news agency said on Wednesday it had seen a letter from the FFF’s ethics board calling on Gueye to explain why he missed Saturday’s game.
The letter, says AFP, calls for him to “issue a public apology” or to say that the rumours he refused to play are “unfounded”.
The letter reportedly adds if he did refuse to play he would be “validating discriminatory behaviour”.
PSG said on Wednesday that they were “very proud to wear this shirt”.
“The biggest stars of world football were on the field on Saturday and expressed the club’s commitment to the fight against homophobia and all forms of discrimination,” it added.
Gueye’s stance has been supported by prominent politicians in Senegal.
The country’s president Macky Sall wrote on Twitter that Gueye’s Muslim beliefs must be respected, while sport minister Matar Ba wrote that Gueye was backed by his country’s people, alongside a picture of the midfielder on pilgrimage to Mecca.