Edinson Cavani could be set for a disciplinary charge after using a racial term on social media.
Cavani took to Instagram to celebrate his match-winning performance off the bench, with one post on his stories replying to a message of congratulations, the 33-year-old used the Spanish term 'negrito', which translates as 'black'.
United stressed that the word was clearly used in an affectionate manner and has different connotations in South America, where Cavani is from.
The club said the 33-year-old had been made aware such terms are perceived very differently in the UK and he subsequently deleted the post.
The Football Association issued guidelines ahead of this season clamping down on racist and discriminatory language and behaviour, with offences on social media carrying a minimum three-game ban.
Manchester City's Bernardo Silva and Dele Alli of Tottenham were both suspended for one match last season after posts that breached FA guidelines.
PA also contributed to this report