City boss Mancini appeared totally stunned in the aftermath of Saturday's defeat to United, when Paul Scholes headed the winner 20 seconds from time.
It was the third occasion this season the Blues had been beaten by a stoppage-time goal from Sir Alex Ferguson's men, who clearly are not intent on relinquishing their long-held Mancunian supremacy without a fight.
But, as Ferguson pointed out in the build-up, City have a wider perspective on their tussles. The end game for Mancini and his boys is a Champions League place, which means the latest loss to United can be overcome.
"If we get fourth this will be forgotten - that is football," said the Dutchman.
"If we can get into the Champions League, no-one will be complaining about the four games against United.
"Losing at home to United is going to hurt. But we are still in the fight. We have to try to bounce back and show people what a great team we are."
In fact, City could take heart from their performances against Ferguson's team. Whilst a solitary success in the first-leg of that thrilling Carling Cup semi-final represents scant reward for so much effort, in taking United so close in all their other meetings, the Blues have made their own statement.
As De Jong points out, this is a new team, built virtually from scratch at the start of last season.
"It is no fluke that we have done well against United in four games this season and playing well against a top side gives you confidence," he said.
"We are all new to each other. It is not like we have had two or three years to grow. We are still close to fourth with four games left."
Having lost their advantage to Spurs, City's task is to match Tottenham's results in their next two matches to set up a mouthwatering confrontation with Harry Redknapp's men at Eastlands on May 5.
"The Tottenham game looks more and more like the crunch," said De Jong.
"But we have Arsenal and Villa before that, so they are pretty big games, especially Villa because they are direct opponents for fourth place.
"People are forgetting about Liverpool but they are still out there as well, so we need points, or one of the other teams will get them and take fourth themselves."
