But away from the Premiership City still have a lot to prove, with Tuesday's must-not-lose Champions League trip to Napoli looming.
Words are easy to say, but Mancini has made a rod for his own back, and I'm sure Barca and Real will remember them should they clash before the final (or AT the final) in May.
How good are City? Like Newcastle, that question has been asked all season, and today we found out.
Yes the 'Money Men' defeated Mike Ashley's 'Bargain Bin' fighters; but how big was the gap?
Toon's fans shared the amusement of a club that just announced losses of £194.9million being forced to announce that there would be "no chips available at half-time".
Mario Balotelli and Sergio Aguero, both scored from the spot in between a rasping finish from home-grown defender Micah Richards (pictured right), who had been overlooked for the England squad last week.
Even Joey Barton took time off from pulling the piss out of Ashley on Twitter to tell the England manager: "How can Capello possibly overlook Richards? Defies belief!"
The win maintained City's 100% home record in front of a stadium record crowd, although Alan Pardew's men could justifiably feel the scoreline did not pay due reward to their own efforts, even after Dan Gosling's consolation.
However, if Demba Ba had profited during United's best spell of the opening period, they might well have headed back to the north-east in even more buoyant mood.
Instead, his snap-shot after being set up by Hatem Ben Arfa was turned away by Joe Hart before he glanced a header wide from Yohan Cabaye's corner.
It was Ben Arfa's first Premier League start since he broke his leg in a challenge with Nigel de Jong in the corresponding fixture last season.
The pair have since made up from what Ben Arfa felt was a nasty tackle by De Jong and thankfully there was no hint of a repeat.
It does seem City have moved forward since then both in personnel and a more expansive style.
Yet again, they were the team carrying most of the threat and before Newcastle's purple patch, Aguero fizzed a shot over the bar and Tim Krul produced an excellent one-handed save to deny Balotelli's close range header.
The Blues were still searching for some kind of inspiration when Ryan Taylor made his intervention.
He would be correct in claiming he was within close proximity of Yaya Toure's shot five minutes before the break.
However, referee Chris Foy presumably took the view that with his arm outstretched, Taylor was asking for trouble, which duly came in the form of a penalty when the ball hit him inside the box.
Never one to avoid a bit of drama, Balotelli strode slowly to the spot-kick before side-footing neatly into the bottom corner.
It was the Italian's ninth goal of the season and was celebrated with a folding of the arms and a steely stare.
Taylor's afternoon was soon to get worse as on City's next attack he tried to control Samir Nasri's through ball and turn at the same time.
All the full-back succeeded in doing was allow Richards the chance to intervene.
Mystifyingly overlooked by Fabio Capello, the full-back finished smartly and suddenly City were clear.
To their credit, Newcastle refused to let their heads drop.
But the second-half just brought more anguish in their bid to drag themselves back into the game.
First Ben Arfa drove a low shot against a post after he had nipped in to rob Vincent Kompany.
Then Fabricio Coloccini belted a volley wide after being picked out completely unmarked from Yohan Cabaye's corner.
Finally, Hart denied Guthrie, who has sped into the box and gone for the far corner from an acute angle.
Having come through those trials and tribulations unscathed, it seemed harsh that City should grab another themselves after Ben Arfa had sent Richards tumbling in the box.
With Balotelli replaced by David Silva, Aguero took over spot-kick duties and promptly sent Krul the wrong way.
The sight of Aguero and Toure hobbling off before the end would be a worry for manager Roberto Mancini with Tuesday's fixture with Napoli looming.
And the City boss would not be too happy that Gosling's effort two minutes from time denied his side a clean sheet.
Source: FOOTYMAD
