The Football Association confirmed on Monday that it will take no action in regard to the allegation.
Footage on YouTube emerged which appeared to show Fellaini spitting near to Zabaleta's head while the City defender lay on the floor following a clash between the pair.
It is understood referee Michael Oliver did not mention the alleged spit in his match report, but the FA could have opted to retrospectively punish Fellaini if it had felt he had been guilty of misconduct.
Oliver booked Fellaini moments before the alleged spit towards Zabaleta for an elbow on the Argentina full-back.
After the 3-0 win, Zabaleta claimed Fellaini was lucky to stay on the pitch.
"I was elbowed by Fellaini. It was a red card," he said.
United manager David Moyes said last week he had discussed the allegation with Fellaini and said the Belgium international is adamant that he did nothing wrong.
"I've spoke with Marouane and he says it isn't the case," the Scot said.
"We will work with the FA if that is what we have to do. Marouane is adamant that at no time did he (spit at Zabaleta). I don't think it is completely conclusive, from what I've seen."
- Sports & Recreation
- Michael Oliver