United got off to the perfect start, an early ball from Ronaldo caught City napping and Rooney drilled a low finish beyond Nicky Weaver with just six minutes gone. City steadied the ship and Micah Richards went close to an equaliser before more hesistant defending allowed the Reds to double their lead, Saha turning home from close range after Gabriel Heinze had won possession.
Stuart Pearce's Blues threatened a comeback in the second half, Hatem Trabelsi's fine effort made for a grandstand finish but Ronaldo made the points safe after Dunne failed to deal with Rooney's teasing centre. The visitors' misery was compounded late on when Bernardo Corradi was shown a second yellow card. The win took United nine points clear of Chelsea at the Barclays Premier League summit, and Sir Alex's team were to win back their crown from Jose Mourinho's side at the end of the season.