A Vincent Kompany header saw city drawing level with United, as Mancini’s side went ahead on goal difference
With Fortyfive minutes played, Kompany rose above Chris Smalling to head home the winner,leaving United chasing shadows in the second half.
United started with Rooney alone up front, Ji-Sung Park playing alongside Giggs, Scholes, Carrick and Nani in midfield with Smalling and Jones replacing Evans and Rafael in the back four.
After a first half virtually devoid of action, City were ahead just before halftime.
A David Silva corner was missed by Chris Smalling, leaving Vincent Kompany free in the box – the City captain made no mistake, heading his team into the lead.
The second half saw United tryin to
claw back the deficit, with Welbeck, Young and Valencia replacing Park, Scholes and Nani.
United were never close to an equaliser though, as City ran away with a 1-0 win which seals a 7-goals lead for them.
City still have to play Newcastle away, while United face Swansea and Sunderland.
The race is still on, with City facing Newcastle away and QPR at home.