Republic of Ireland midfielder James McClean faces a possible fine after pumping his fist in front of Sunderland fans following West Brom's 1-0 home win on Saturday.
McClean, a former Sunderland player, was subjected to abusive chants from the away fans over his refusal to wear a Remembrance Day poppy on his shirt while at the club.
After the final whistle at the Hawthorns on Saturday, McClean ran towards the travelling support and made the gesture.
Sunderland players Danny Graham and Fabio Borini led a group of angry players who confronted McClean, leading to others from both sides becoming involved.
McClean later posted a photo of his celebration to Twitter.
— James McClean (@JamesMcC14) October 18, 2015
McClean (26), from Derry, previously made headlines when he snubbed the British national anthem during West Brom's USA pre-season tour in the summer.
He has become known for refusing to wear a poppy on his shirt in the run-up to Remembrance Day. In Saturday's matchday programme, he again explained his stance on the issue.
"If the poppy was simply about World War One and Two victims alone, I would wear it without a problem. I would wear it every day of the year if that was the thing."
"But it stands for all the conflicts that Britain has been involved in. Because of the history where I come from in Derry, I cannot wear something that represents that.
"I have no issue with people who do wear a poppy. I absolutely respect their right to do that but I would hope people respect my right to have a different opinion on it too."
Great win today, lads were excellent, fans were excellent have a great weekend baggies fans
— James McClean (@JamesMcC14) October 17, 2015