Leo Messi inspired FC Barcelona to trash ManCity 4-0 at Camp Nou in Champions League Group stage.
Messi opened the scoring just after the quarter-hour mark, but for much of the opening period Manchester City played well, justifying Guardiola's decision to line up in what amounted to a 4-6-0 formation with Sergio Aguero left on the bench.
They might even have got back into the match if it hadn't been for a dreadful error by goalkeeper Claudio Bravo, who spooned a pass straight to Luis Suarez while well outside the box - and foolishly handled the ball as Suarez tired to lob it back over his former team-mate's head.
Bravo was red carded instantly, and down to ten men City were then torn apart with Messi scoring twice in the next fifteen minutes.
Neymar missed a late penalty which would have made it four - but made up for his weak spot kick by slotting the fourth home in the penultimate minute.