After the joy and wonder of an Olympic fortnight that will never be forgotten, English football delivered an ugly opening to the new season.
Second-half goals from Toure, Tevez and Nasri gave the Premier League champions their first Shield triumph since 1972.
But it was the succession of niggly tackles, eight yellow cards and a straight red for Branislav Ivanovic that left the biggest impression as Chelsea lost out, despite Fernando Torres and Ryan Bertrand scoring the first and last goals.
The community aspect of this game was missing from the first whistle as referee Kevin Friend struggled to keep control.
Stefan Savic was booked after 10 minutes, which set the scene for a niggly opening period in which both sides were guilty of going too far at times.
Ivanovic was the worst offender. Forced to challenge for a stray John Terry pass, the Serbian slid straight into countryman Aleksandar Kolarov, studs raised.
It was not two-footed, but it was dangerous. And though Chelsea protested, Friend was justified in dismissing Ivanovic, who must now miss next week's trip to Wigan, plus home encounters with Reading and Newcastle.
Earlier, David Luiz had been cautioned followed by Frank Lampard, and in the immediate aftermath of Ivanovic's exit, John Obi Mikel.
In addition, Savic raised an eyebrow when he flattened Torres in an incident Friend chose to see as a free-kick in favour of the Montenegro defender when it was not inconceivable the decision would go the other way, with dire consequences.
It amounted to some introduction into English football for one-time City target Eden Hazard.
There are immediate comparisons to be made between Hazard and former Blues favourite Joe Cole in both appearance and running style.
The Belgian evidently has plenty of guts too.
Targeted by the City faithful over his summer snub, Hazard had the character to respond when he attempted a back-heel at full speed and met only with a comical fall headlong into the turf, having got his manoeuvre badly wrong.
Hazard was a bystander when Chelsea got their opener.
Ramires created it, nipping past Pablo Zabaleta before surging into the box and flicking an astute pass past Hazard to Torres on his right.
The £50million man showed signs last season of starting to find his old form and, with Didier Drogba embarking on his new life in China, manager Roberto di Matteo needs Torres to justify that massive price tag.
Today's contribution was clinical, beating the advancing Costel Pantilimon with the predatory instinct of old.
Pantilimon had been given a rare start due to Joe Hart's back injury and having been the least busy of the two keepers, probably felt hard done by.
Carlos Tevez, Samir Nasri and skipper Vincent Kompany had all gone close for the Premier League champions.
As so often on showpiece occasions, though, Toure was the man who did the damage.
Seizing on John Terry's poor clearance, the midfielder drilled a fierce shot straight back through a crowd of bodies, giving Petr Cech no chance of keeping it out.
Now City had the momentum with them and made their extra man tell.
Six minutes later, neither Luiz nor Terry were able to check Tevez's darting run along the edge of the penalty area.
From a central position, Tevez belted a superb shot into the top corner to put the champions ahead.
Six minutes after that, City scored again as Kolarov streaked past makeshift right-back Ramires and curled a cross to the near post which Nasri touched home.
If Ramires had not managed to steer James Milner's cross over the bar, an unmarked Tevez would have had a tap-in as a rampant City poured forward.
Yet it was Chelsea who scored 10 minutes from time, through substitute Bertrand, who promptly became involved in a spat with Pantilimon as he tried to wrestle the ball away to restart the game.
City came closer to grabbing a fourth than Chelsea an equaliser though, as Sergio Aguero somehow managed to turn Milner's cross wide in the final minute when it seemed easier to score.
The five goals did amount to decent entertainment. As Ramires got away with a cynical bodycheck on David Silva that should have brought a second yellow, it reminded that the behaviour just reinforced old stereotypes football needs to shed.