October 23, 2011. It was one of the darkest days for Manchester United, who lost 6-1 to Manchester City in a rout at Old Trafford. United legend Wayne Rooney became embroiled in controversy after the game when it was revealed he was out partying with City players following the hammering and the England icon has now revealed why.

The match had been set up to be a tight clash, but Roberto Mancini registered one of the most iconic derby wins in the history of the Premier League. City's super team included the likes of Yaya Toure, David Silva and Sergio Aguero amongst others.

It was the first Manchester derby in history where the clubs faced off while being in first and second place in the league table. United boasted Wayne Rooney, Nani and prime Ashley Young but they were no match for a rampant City side.

"After something like that I'd usually just go home. But I had a birthday party. Joe Hart, Gareth Barry and a few of the City players were invited to my birthday party," he said on BBC's The Wayne Rooney Show.

"You've got family, friends, everyone who's made their own plans to come. I was like, 'I can't cancel it' so I went.

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"We've got the United lads, some of the City lads sat there. I think it was me, Crouchy [Peter Crouch], Harty [Joe Hart] - we all got up and did a song of Backstreet Boys.

"Looking back, I should have cancelled, but it was the friends and family who'd all booked the time off and got the babysitters and stuff."

In the game, Mario Balotelli opened the scoring on the 22nd minute with a lush side-footed finish into the bottom right corner. He then produced his now-infamous 'Why Always Me?' celebration. It was 1-0 at half time but things got worse after Jonny Evans was red-carded shortly after the restart.

Balotelli would score again on the hour mark before Sergio Aguero but the visitors 3-0 up 10 minutes later. United had claimed a goal back through Darren Fletcher, now interim boss of the club, on 81 minutes, but the final 10 minutes were a car crash for United.

Edin Dzeko got a brace and David Silva scored to see City bag three goals in only four minutes to really rub salt into the wounds of United fans and players.

Speaking about the result itself, Rooney said: "I think that was a big moment for City back then because you could feel City coming up and getting closer to us.

"But to come to Old Trafford and win 6-1, I think that was a statement. I remember being on the pitch and it was horrible. It was like in the second half, just felt like it was goal after goal, and you're just like, 'oh, get me off this pitch'."

City inflicted the biggest-ever Premier League defeat on their rivals and it was the first time since 1930 that United conceded six goals at their home ground.