They were never in any real danger of suffering one of the greatest cup upsets of all time, with goals from Dimitar Berbatov, Michael Owen and Antonio Valencia wrapping up victory shortly after half-time at the EBB Stadium.
Manager Ferguson told Sky Sports afterwards: "Obviously, we had a difficult day on Sunday simply because we tried to play the history book.
"The nature of Manchester United is to go and win the game, whether it's eight men, nine men, 10 men or seven men.
"That's their nature and it's very difficult to change that.
"But tonight they kept their discipline, they kept their professionalism, enjoyed it tonight - the players enjoyed that."