The FA is expected to investigate a social media post by Manchester United striker Edinson Cavani.
The Uruguayan international shared an Instagram story from a fan, using a racially offensive term. The post has since been deleted.
Manchester United and the FA did not wish to comment on Sunday night, but Sky Sports News understands the governing body will launch a probe into the online post.
Facebook, the owners of Instagram, have been approached for comment.
Cavani came off the bench to score twice in United’s dramatic comeback victory against Southampton at St Mary’s.
The Uruguay international also assisted Bruno Fernandes for their first goal in the 3-2 win which saw Ole Gunnar Solskjaer’s side seal their fourth consecutive away Premier League win.
The 33-year-old has now scored three league goals for the club since joining as a free agent in the summer transfer window.
Solskjaer waits on De Gea injury but praises Henderson
Manchester United goalkeeper David de Gea was withdrawn at half-time against Southampton after suffering a knee injury.
The Spain international was replaced during the break by Dean Henderson, who has been struggling for game time since returning to the club from his loan spell at Sheffield United.
Solskjaer admitted he was hopeful De Gea would be available for Wednesday’s important Champions League clash with Paris Saint-Germain – but took the opportunity to praise the Spaniard’s stand-in.
“Let’s have a little check on [De Gea],” Solskjaer told Sky Sports. “Hopefully he will be ok for Wednesday but I’m not sure.”
“Dean played well though. He is a ‘keeper who is used to being vocal. He wants to organise his team. He didn’t have big saves to make but he was safe with his hands.”