The Football Association has confirmed it is looking into an incident involving James McClean and sections of the crowd during Stoke's clash with Middlesbrough as well as a social media post in the aftermath.
Derry-born McClean, backed by his club, chose not to wear a poppy on his shirt during Saturday's game, just as he has done in previous years since his arrival in England with Sunderland in 2011.
The Republic of Ireland international has regularly gone public with his reason behind not wearing a poppy, but he was still booed by sections of the home crowd at the bet365 Stadium.
McClean, who had come on as late substitute, then appeared to remonstrate with visiting supporters and launched an emotional response after the game, slamming fans as "uneducated cavemen".
His post on Instagram on Sunday will be looked at by the FA before a decision is made on any disciplinary action.
Stoke stated last week that they "respect his decision and his right to follow his own convictions" after McClean confirmed he would not wear a poppy on his shirt against Boro and when they face Nottingham Forest on Saturday.
Before the weekend's flashpoint, McClean said: "I know many people won't agree with my decision or even attempt to gain an understanding of why I don't wear a poppy.
"I accept that but I would ask people to be respectful of the choice I have made, just as I'm respectful of people who do choose to wear a poppy."