Wayne Rooney was so focused on victory in Manchester United's derby clash with Manchester City that he forgot he had just scored his 100th club goal.

The striker's tap-in, three minutes before half-time after Joe Hart had parried Michael Carrick's angled drive into his path, allowed United to claim the points despite having Cristiano Ronaldo sent off for a bizarre second booking for handball.

The result was revenge for United after City completed a domestic double over their neighbours last term and allowed Sir Alex Ferguson's side to take maximum advantage of Chelsea's shock home defeat to Arsenal.

It also enabled Rooney to move into three figures in a career that started with Everton, even if the 23-year-old was not instantly aware of what he had done.

"I didn't think about it being my 100th career goal," he said.

"It was more the fact that it was City away. For it to be the winning goal as well really made it something to be pleased about.

"But of course it is a great achievement. I am delighted to reach 100 and, as I have said before, I am looking to score more often."

United completely bossed the first half and looked set to stroll home until Ronaldo saw red.

The winger, who is expected to collect the Ballon D'Or this week, inexplicably parried Rooney's corner with his hands, leaving referee Howard Webb little alternative other than to dismiss him on the same ground where he was sent off three seasons ago.

"He was trying to protect himself from the ball hitting him in the face," said Ferguson.

"He thought he had heard a whistle and he got a push as well.

"The crowd played a part and he got sent off. Sometimes you have to overcome these things and we overcame a lot today."

As Ronaldo is banned for Wednesday's Carling Cup encounter with Blackburn at Old Trafford, when he would not have played anyway, his misdemeanour has not proved costly.

Of more significance will be Patrice Evra's absence from the league match at Tottenham on 13 December after the French full-back collected his fifth booking of the campaign.