Following United's 3-0 defeat on Tuesday, footage emerged on the YouTube website appearing to show midfielder Fellaini spitting near Zabaleta's head while the City defender was on the turf following a clash between the pair.

It is understood the Football Association are aware of the clip, with the governing body now deciding whether to charge Fellaini with misconduct.

The FA are now due to request sharper footage from match broadcasters Sky before ruling on whether Fellaini should face disciplinary action, with a decision anticipated some time early next week.

But United manager David Moyes, who signed Fellaini from former club Everton, said he'd discussed the incident with the Belgium international and that his player was adamant he'd done nothing wrong.

"I've spoke with Marouane and he says it isn't the case," Moyes said.

"We will work with the FA if that is what we have to do. Marouane is adamant that at no time did he do that (spit at Zabaleta). I don't think it is completely conclusive, from what I've seen," the Scottish boss added.

Earlier this month, the FA banned Hull's George Boyd for three matches after he spat at Manchester City goalkeeper Joe Hart.

Moments before the alleged spitting incident, Fellaini was booked by match referee Michael Oliver on Tuesday for elbowing Argentinian full-back Zabaleta.

After the match, Zabaleta said Fellaini was fortunate to remain on the field.

"I was elbowed by Fellaini. It was a red card," he said.