United fell behind in the 38th minute as Joleon Lescott nodded the Blues into the lead and Edin Dzeko added a second from some 30 yards out just moments before referee Phil Dowd blew for half-time.
After the break, United responded with a Chris Smalling goal, followed by two goals from Man of the Match Nani, with the first capping off a quite incredible passing move by United as the impressive Tom Cleverley claimed an assist on his official debut for the club.
Despite the half-time deficit, Rooney claims he and his teammates remained confident, but conceded that the victory wouldn’t have felt quite as sweet had it not been City on the other end of the defeat.
Speaking to the SkySports cameras, Rooney said: “Yeah of course [It’s sweeter when you beat City]. I think there was only one team who looked like winning that and we dominated from start to finish.
“They scored two goals from nowhere, but we still had enough to win the game.”
The match saw seven yellow cards handed out with City winning that particular duel 5-2, however the England international was quick to point out the match was never in any danger of getting out of hand with tempers never looking to flare as they had last time the two sides met at Wembley in last year's FA Cup semi-final.
“There were no malicious tackles in the game,” he explained. “A few fouls, but that is something you have to deal with, but that was about it. Both teams went for the win and it was well-earned.”