Sunderland manager Martin O'Neill confirmed James McClean has been a target of death threats after the winger decided not to wear a Remembrance Day poppy on his shirt.
The Republic of Ireland international opted against wearing the symbol during the Black Cats' 2-1 defeat at Everton last weekend.
McClean, 23, was introduced as a second half substitute during yesterday's match against Fulham and received a few jeers.
O'Neill said: "James will deal with it (the booing). I think it is to do with the issue last week, it's a free choice in this world. James has lived with a lot of things - he's getting death threats too now so that doesn't help."
It is understood that police are investigating the threats which were directed towards McClean on Twitter, although the player no longer uses the social networking site.