The 23-year-old was booed by a section of his own fans when he came off the bench during his side's 3-1 victory at Fulham on Sunday.

McClean refused to wear a poppy during Sunderland's 2-1 loss to Everton on November 10 and O'Neill said the Irishman had been threatened.

"James will deal with it. It's to do with the issue of last week (not wearing a poppy). It's a free choice here in this world," O'Neill told reporters.

"James has lived with a lot of things. He's getting death threats now."

Sunderland claimed a much-needed victory against Fulham, with the hosts reduced to 10 men in the first half following Brede Hangeland's dismissal for a challenge on Lee Cattermole.

Steven Fletcher, Carlos Cuellar and Stephane Sessegnon all found the back of the net for the away side to give the scoreline a convincing look.

But O'Neill admitted that the sending off played a major part in his team's victory.

"The sending off of course changes the dynamic of matches. You saw it yesterday with Tottenham and you have to try and take advantage of that and I thought we were able to do that in the second half yet we were never able to put Fulham away," he said.

"We've been given the directives. I didn't know how many times we need to be told about it. We've been guilty ourselves with Cattermole getting sent off but sometimes I don't understand players now.

"There is a better chance of winning a football match with all your players."

Fulham manager Martin Jol disagreed with O'Neill and said the red card awarded to Hangeland was harsh.

"I think he (referee Lee Probert) was probably the only one in the stadium who really thought it was a red card," he said.

"It would have been nice if most of the referees had played football themselves, it would be nice if sometimes they could make decisions in the spirit of the game.

"I can't remember having a red card at this club, he (Hangeland) is a nice boy and told me it was not intentional, he slipped.

"I won't say that it is a common thing for him because I haven't seen him do this tackle."