United manager Sir Alex Ferguson said it is the title decider and the most important derby he has faced in his 26 years at the club given his side are three points clear of their rivals at the top with three games left.
His rival Roberto Mancini reckoned former United striker and rehabilitated City returnee Carlos Tevez is "destined to score the most memorable goal in the history of this club".
It is all set for quite a showdown. Hours before kick-off there was a real air of excited anticipation in the streets of the city centre.
Souvenir sellers were already in place selling "half-and-half" scarves, prominently displaying "Manchester City v Manchester United, April 30 2012" woven into their fabric while huge City and United flags fluttered above their stalls.
A local ticket agency advertising two tickets for the match said they were some still available at 1,500 pounds each "with an unobstructed view of the pitch" while bookmakers Ladbrokes said they were expecting to take more than 100 million pounds in bets, the biggest figure on a single match in England.
There was a steady stream of fans heading early to the east of the City where City's stadium is situated.
There were countless fans of all shapes and sizes wearing City's light blue colours and United's red in amongst the shoppers along the central street of Deansgate, where Mancini and assistant Brian Kidd were seen taking a lunchtime stroll.
The Manchester Evening News declared simply "Day of Destiny" on its front page and "Legends or Losers" on its back.
A win for United will almost certainly see them clinch the title for a record-extending 20th time, while victory for City would put them on course to win the League for the first time since 1968 and prove they really are now United's equals.
Backed by the vast fortunes of Sheikh Mansour of Abu Dhabi, they have come a long way since the dark days when they dropped into the third tier just over a decade ago.
City have invested an estimated billion pounds plus in trying to catch United, but if they lose on Monday, another huge investment looks likely over the close-season.
The hosts have been in excellent form since Tevez made his peace with the club after falling out with Mancini after refusing to warm up as a substitute in a Champions League match at Bayern Munich in September.
Since returning to the starting line-up, the Argentina striker has scored four times in three matches.
United have stumbled of late with a loss against Wigan Athletic and last week's 4-4 home draw with Everton meaning City have the momentum going into the 146th league clash between the two.
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