What a humiliation for Sir Alex Ferguson and his side who, in losing 6-1 to their nearest and not so dearest rivals, suffered their heaviest defeat since the inception of the Premier League — and conceded six goals at home for the first time since 1930!
Those ‘noisy neighbours' have a lot to shout about now, don't they Fergie?
City are top dogs and with the high quality players at manager Roberto Mancini's disposal, plus all that finance if he needs to strengthen his squad in January, it's hard to see anyone stopping them in the title race.
United may disagree, but there's no question they are up against it, five points behind a side whose confidence will soar after their resounding success at Old Trafford.
Yes, United played most of the second half without Northern Ireland's Jonny Evans, who was correctly sent off moments after the break for a senseless foul, but this was still a huge embarrassment for them in what a stunned Ferguson described as their “worst ever day”.
Even before the red card, City were ahead thanks to a classy Mario Balotelli first half strike and in control of the game.
After the Evans dismissal, the visitors ran riot, scoring through Balotelli again, Sergio Aguero, substitute Edin Dzeko twice and the magnificent David Silva.
The scoreline could have been even worse for United in the 160th Manchester derby, as they were outclassed by a City side showing no ill-effects from the ongoing Carlos Tevez saga.
Scottish midfielder Darren Fletcher curled home a beauty for the home team with nine minutes left to make the scorline 3-1 but, instead of acting as a launchpad for another famous United comeback, it spurred City on further to rip an overstretched and error strewn defence to pieces in the dying stages.
To think that Ferguson's team started brightly, but they lacked a cutting edge and incisive final ball to make the breakthrough.
There were no such problems for Mancini's men on 22 minutes when Silva and James Milner manufactured an opening for Balotelli who, afforded too much space by Evans, brilliantly stroked the ball into the net from just inside the box.
It was a fantastic finish from the Italian who, too often since moving to Manchester, has hit the headlines for all the wrong reasons, including recently accidentally setting his house ablaze with fireworks.
He was on fire himself yesterday, displaying a tee-shirt with the words ‘Why Always Me?’ to celebrate his opener. That earned him a booking.
More importantly his goal gave City belief. From then on they were the superior team — against 11 men and then 10 due to the Evans sending off which came on 47 minutes when he lost concentration and then his man, pulling back Balotelli as he threatened to race clear.
City went from strength to strength after that.
It was only a matter of time before they would score again and they did through Balotelli on the hour from close range after excellent approach play by the sensational Micah Richards, superb Milner and sublime Silva.
Nine minutes later Balotelli, Richards and Milner created number three for Aguero and, although Fletcher cut the deficit, City went on the rampage in the dying minutes of this game.
In the 90th Dzeko scored from a couple of yards after United's defence went AWOL from a corner and then, twice in injury time, the visitors broke with menace allowing Silva and Dzeko to complete the rout and inflict United's first home loss in 38 games.
City fans still talk about that memorable 5-1 victory over United at Maine Road in 1989 but, as the years that followed proved, it was the exception rather than the rule during Ferguson's trophy laden reign.
Make no mistake about it though, yesterday's 6-1 win is different.
The balance of power is shifting.
It might take United some time to wrestle it back.
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