Then the wheels fell off the Black Cats’ bandwagon.
One nonchalant swing of Toure’s right leg sent a curling long-range shot beyond the fingertips of Mannone after 55 minutes and two minutes later Nasri met Aleksandar Kolarov’s half-cleared cross with an unstoppable shot.
It was cruel on Sunderland, but they refused to capitulate and once their heads had cleared from the shock of two lightning bolts they began to pose some serious questions of a City defense that still looked vulnerable.
With Sunderland throwing men forward substitute Steven Fletcher hit a shot straight at Pantilimon and they battled gamely until the end to no avail.
Substitute Navas made absolutely sure there was no way back for Sunderland with a clinical third on the stroke of fulltime.