Mancini conceded defeat in the title race after falling 15 points behind and a deserved success did little to change his mind. Sergio Aguero scored a sublime winner as City at least made a point to their neighbours. City had led early in the second half through a deflected James Milner strike before Phil Jones forced Vincent Kompany to turn into his own net.
When asked if the result could affect United's confidence ahead of their final seven games, Mancini said: "United? No. The championship is finished. But we deserved to win because we played better, we played good football. We didn't take any risk."
Mancini feels City proved with their defeat of United they are capable of challenging for title glory again next season. Mancini said: "We need to continue to play like this for next season. We have two or three months where we can work well, where we can improve our team. I think we showed we can't be 15 points behind.
"But we can say United won a lot of games. They lost their last game against Norwich a long time ago and they deserve to win this title, for sure."
Sir Alex Ferguson claimed that Manchester United were merely reverting to type by losing at Old Trafford. Whilst victory would have taken them to the brink of a record 20th league title, a loss means they will have to wait at least a couple of weeks for confirmation of their status as Premier League champions.
"If you look at the history of our club, we always make it difficult for ourselves," said Ferguson. "We have our supporters hanging on the edge of their seats every year. We have a 12-point lead but we won't be taking anything for granted. The plus point is that we only have seven games left now. As each game goes along you whittle them down.
"We have Stoke on Sunday. The support will be great and we will have a go. We have to kick on now."
The United boss did feel Carlos Tevez was interfering with play from an offside position when man-of-the-match Milner drove City in front. However, Ferguson felt he had a contender for the game's best player in Jones, who was outstanding in central defence.
"Phil was magnificent," he said. "He has only played two games at centre-back this season. That tells you what a good player he is. The boy could be anything. At 21 he is a man."
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