City skipper Vincent Kompany suggested after the derby demolition that his side had maybe wanted the win more than their United counterparts.
Rooney was one of the only United players to come out with any credit and Zabaleta believes his work-rate in the game dispelled Rooney's claim that Liverpool represented a bigger match for United than taking on City.
"I saw Rooney. He was one of their main players, he tried more than anyone else in the Manchester United team," admitted Zabaleta
"He says Liverpool is still the big game. But I saw him working so hard, so probably it proves this game is just as important to him as United against Liverpool.
"When the game is like that, and you see the team playing like that against a team like Manchester United, you know it's a special game."
Zabaleta also believes the win over United will boost the confidence of new boss Manuel Pellegrini and the club's new signings as they look to regain the Premier League title this season.
"This result has helped the manager, his staff and all the new players," said Zabaleta.
"Winning like that gives you confidence.
"It should help the team to play much better collectively than we have done.
"If we carry on playing like that in such a big match, we have a lot of chance to fight for the title.
"But we have to be ready to play every game the same way. Sometimes we talk about mentality and focus on every game in the Premier League because we know how important it is.
"It is true the way we played in the last games was different so we must try to keep the same intensity as it was against United."