Manchester United's Wayne Rooney (left) and Javier Hernandez (second left) react during their English Premier League match against Manchester City at Old Trafford in Manchester, northern England, on Sunday. Man City crushed arch-rival Man U 6-1. Darren Staples / Reuters

Sir Alex Ferguson insists Manchester United will recover from the worst result of his career after the Premier League champion was thrashed 6-1 by Manchester City at Old Trafford.

The extraordinary defeat represented City's biggest win at Old Trafford since January 1926 as Mario Balotelli and Edin Dzeko claimed two goals each, with further strikes from David Silva and Sergio Aguero.

Table-topper City is now five points clear of bitter rival United after a remarkable day in the history of both clubs.

It was the biggest defeat suffered by Ferguson in his illustrious 54-year career as a player and manager, and also United's heaviest Premier League loss.

However, Ferguson, who blamed the defeat on the dismissal of defender Jonny Evans moments into the second half, expects United's players to show their character and bounce back in the League Cup tie at Aldershot on Tuesday.

"I'm shattered, I can't believe it," Ferguson said. "It was an incredible disappointment. We played some brilliant football in the first 10 minutes.

"It was hard to believe we were 1-0 down but that's retrievable. The sending off was the killer blow.

"After that we kept attacking. It's alright playing the history books but common sense has to come into it. When we went to 3-1, 4-1 we should have settled for that.

"But you have to recover. The history of Manchester United says we will recover.

"That kind of defeat will make an impact on the players. There's a lot of embarrassment in that dressing room and quite rightly so."

The defeat proved doubly costly for United, which has now fallen far behind City in the goal difference column, trailing City by 12.

"It's the manner of the defeat," Ferguson said. "And the goal difference. Over the years we have always enjoyed a better goal difference than our rivals but today we are well short."

The mood was clearly different in the City camp with manager Roberto Mancini even breaking into a smile when asked about the latest antics and controversy to engulf Balotelli.

Balotelli made headline news on the morning of the game after the fire brigade were called to his Cheshire home to put out a blaze early on Saturday caused by fireworks being let off in his bathroom.

Mancini believes Balotelli, who was also booked for celebrating a goal by displaying a T-shirt with the slogan 'Why Always Me', has the ability to become one of the world's leading players if he can curb his off-field behavior.

City is now well placed to win its first title since 1968 although Mancini, keen to keep a lid on expectations, insists his club is not necessarily a strong favorite.

"I think there are four or five teams that can win the title in the end," he said.

"The season is too long, it is very difficult every game, every three days we play.

"United are too strong for this. They know, like me, there are only three points. This is only one game. I still think United are one yard above us.

"I think we can only change this after we win the title in the end. After, maybe it will be different, but now United are better than us.

"I have big respect for Sir Alex, I have big respect for United because we are talking a top manager and a top squad. I don't think (win) this is important."