Here are four things we learned from the game at Old Trafford...
1 Maffeo can challenge senior stars
Pablo Maffeo was one of the stars of the show against United, delivering a solid performance at right-back and keeping the in-form Marcus Rashford quiet for much of the game.
It was a timely reminder of his capabilities. Bacary Sagna is currently out having suffered a hamstring tear playing for France earlier this month and Pablo Zabaleta is still recovering from a foot injury sustained against Barcelona.
Maffeo, 19, gave a display that suggests he is ready to step in on a more regular basis.
2 Garcia possesses real quality
Another 19-year-old also impressed.
The Spanish youngster sat deep and sprayed the ball around, demonstrating his ability to pick passes, both long and short, and keep City in possession.
Guardiola, a man obsessed with build-up play, will no doubt have been hugely impressed.
3 Rotation should leave Blues squad fresh
With City facing a packed fixture schedule in the coming weeks, it made sense for Guardiola to freshen things up for this game.
Nine changes were made from the side that drew 1-1 with Southampton at the weekend.
That should benefit the squad with games coming thick and fast.
4 City need a result
It’s now six matches without a win for City – the first time since 2008 they have endured a winless streak that long.
The good news for Guardiola is the quality of City’s football during that period has largely been impressive.
A win is needed, though. Next up: West Brom on Saturday.