As always, City were finding it sticky going in their Premier League clash against the Toffees.
Balotelli's introduction after an hour changed all that, the Italian's shot flying in off Phil Jagielka to put the Blues on the way to a precious home win that was sealed by Milner in the final minute.
There could not be a greater contrast between City's vast wealth and the relative hand-to-mouth existence of their north-west neighbours.
Yet Everton are a stoic bunch and despite enduring another summer of fiscal austerity, manager David Moyes has engineered a decent start.
And, of course, there was that amazing record against City to protect. Since Sheikh Mansour completed his Blues buy-out in 2008, the clubs have met on six occasions. Everton have won five, including the last four, proving money cannot buy you everything.
Moyes' masterplan this time was to send Jack Rodwell scurrying around after danger-man David Silva all afternoon.
It was a task Rodwell stuck to gamely, and clearly Silva did not like, even though he responded in textbook fashion, moving himself next to Leighton Baines, in theory creating a huge hole for the remainder of City's midfield to fill.
That they did not manage it was in part due to the cussedness of Phil Neville and Seamus Coleman, who tackled anything that moved, and part due to lacklustre displays from Yaya Toure and Samir Nasri, neither of whom imposed themselves on the contest.
Indeed, there were only 10 minutes of the opening period remaining when Tim Howard was forced into his first save.
It was a good one though, the American parrying away Sergio Aguero's goalbound curling shot despite the not inconsiderable frame of Edin Dzeko closing in.
Howard also denied Gareth Barry shortly afterwards as City began to turn the screw, although by the time referee Howard Webb blew his whistle for half-time, Everton were showing more attacking intent than they had done since the opening moments, when they were actually on top.
The hosts came close to opening their account straight after the restart when former City skipper Sylvain Distin rather unconvincingly combined with Howard to turn Nasri's dangerous cross behind.
Mancini's men were unable to maintain the pressure though, so with an hour gone, the Italian turned to Balotelli, ahead of deposed skipper Carlos Tevez. A very astute move it turned out to be too.
Everton were still reorganising following the exit of Tim Cahill, who had earlier guided a header just over but then came off worst in a challenge with Vincent Kompany that led to him becoming the fourth visiting player booked when the Italian struck.
Aguero was the architect, crabbing in from the right flank before rolling the ball into Balotelli's path as he found his own route into the penalty area blocked.
Without a league goal since February, but becalmed after a pre-season row with his manager in the United States and a scorer in the midweek Carling Cup win over Birmingham, the Italy striker took aim, benefiting from a slight deflection off Jagielka as the ball nestled in the far corner.
The 21-year-old immediately sprinted off to his manager to celebrate, any irritation that has at times existed between the pair currently not in evidence.
Within a couple of minutes, Silva had almost made it two, drilling a low shot against the base of Howard's left-hand post, the Everton keeper knowing he was getting nowhere near it.
Howard was able to reach Balotelli's next effort, a stinging shot from the edge of the area that was heading for the bottom corner.
The Toffeemen were on the back foot though and only an offside flag prevented them conceding a second after Silva had tapped home Balotelli's cross.
Milner eventually secured the win, racing onto Silva's throughball before keeping his nerve to beat Howard in the final minute.