United's players looked all at sea when asked to play an unfamiliar formation and that allowed David Silva to pull the strings for City

It takes a particularly dominant performance from an away side to prompt the home manager to consider changing his system within the opening 10 minutes – but that is precisely what happened as City took control with an astonishingly confident start.

David Moyes was seen preparing Antonio Valencia nine minutes into the game, and while Michael Carrick had taken a knock and was hobbling for a couple of minutes, it appeared Moyes was desperate for an excuse to make a change. The fact it was Valencia being readied, rather than a central midfielder like Darren Fletcher, underlined the fact that the manager would have completely reformatted his midfield.

Moyes had named a surprise starting XI for the game, playing a trio of Carrick, Marouane Fellaini and Tom Cleverley for the first time. That changed the shape of their midfield and the side as a whole – whereas they usually play with two deep midfielders and another connecting the rest of the side with the striker, it was a 4-3-3 with Carrick deepest.

United had no answer for the movement of David Silva as he drifted into pockets of space behind their midfield, before combining with onrushing City midfielders

At least, that is how it appeared – it was difficult to judge considering United were utterly dragged out of shape in the opening 10 minutes. Moyes presumably wanted numbers in the centre of midfield, perhaps to contain Yaya Touré, but David Silva made a mockery of that intention with a stunning display from the No10 position.

From the moment he brilliantly collected the ball to race through United's defence in the build-up to Edin Dzeko's first-minute opener, it was clear the Spanish playmaker was going to shine.

Whereas Silva is usually forced to drift inside from wide positions to provide creativity, as the No10 he is permanently involved in play and can shift from side to side, finding pockets of space between opposition central midfielders, centre-backs and full-backs. Silva's ability to lift the tempo of passing moves, receiving the ball on the half-turn before playing it to fellow attackers, meant United were simply unable to get close to him. He continually played the ball to City's wide players, who received support from the full-backs and overloaded the wide areas.

In the end, Moyes did not make that early substitution. But he did change the system after 10 minutes, with Cleverley pushed out to an unfamiliar right-sided role and Juan Mata becoming the No10. It was neither an attacking nor a defensive switch – it was simply a return to United's usual shape, with Moyes recognising his players were completely lost with the 4-3-3, and required reliable shape and structure. He eventually brought on Shinji Kagawa for Cleverley at half-time, the earliest he could introduce a player comfortable on the right without embarrassing the beleaguered England player.

In fairness, the change of system was successful in getting United back into the game, although the fact Moyes was simply reverting to his standard system, following a surprise starting XI, indicates he was fixing his own mistake. There were flashes of promise: Wayne Rooney dropped away from the centre-backs to cause problems between the lines and Danny Welbeck sprinted in behind from the left, troubling both Pablo Zabaleta and Vincent Kompany. But even then, there wasn't any cohesion to United's play.

The exact opposite was true of City, and while Silva was unable to provide a perfect penetrative pass to complete his magnificent all-round performance, the Spanish playmaker's constant probing continually put pressure upon the United defence, and eventually City extended their lead. Even set-pieces went badly for them – it was obvious City were continually thumping corners into the near-post area, with the taker often pausing to wait for a team-mate charging into that space. The pattern was clear by half-time, yet United left that zone completely open for Dzeko's coolly taken second.

Moyes went chasing the game at 2-0 down, introducing Valencia for Fellaini and shifting Rooney back into a central-midfield role. In truth, United were lucky Manuel Pellegrini responded to that substitution by introducing the holding midfielder Javi García for right-winger Jesús Navas – they no longer possessed such a counter-attacking threat, and Silva was less effective (and defensively suspect) on the right. Still, it meant Touré moved into a more advanced role, and he completed the thrashing.