"We made a lot of mistakes against the wrong opponents, we have to say that they played fantastic football".
Our football writers have their say.
Senior officials at Manchester City have since apologised for the incident and according to reports, they ordered the Madness song be cut short. It was a masterclass - Patrick Vieira dominating midfield, Robert Pires... At the beginning, we played better away than at home.
This gritty success was the ideal preparation for hosting Borussia Dortmund in the Champions League last 16 first leg on Wednesday.
The victory takes City clear of Liverpool on goal difference again, though Liverpool have a game in hand.More news: 72 die from tainted liquor in India
City led 4-0 after 25 minutes as Chelsea lost their third straight away game, conceding 12 goals without reply.
After Aguero had somehow missed an open goal from two metres, the Argentine promptly beat goalkeeper Kepa Arrizabalaga with a blistering strike from 25 metres, underlining the fact that he is far more than a penalty area poacher.
City were helped by the vulnerable nature of Chelsea's defence but in truth few teams would have been able to survive the speed, precision and directness they produced.
Sergio Aguero equalled Alan Shearer's record of 11 Premier League hat-tricks, Raheem Sterling treated himself to a brace and Ilkay Gundogan got in on the act too in what proved to be an unforgettable 90 minutes at the Etihad Stadium.
Sterling completed the rout, turning in a low cross from Oleksandr Zinchenko in the 80th.More news: Grammys 2019: Joy Villa dresses as Trump's border wall on red carpet
"It is one of the worst nights in my career", added defender Azpilicueta, 29. It is hard to explain what happened.
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Pep Guardiola had described this match as a "final" for his side given that Chelsea had a week to prepare, while City ground out a 2-0 win at Everton on Wednesday. Today was not the case.
"As much as we're doing really well and the fans and some of my friends are getting excited, I said "well listen, when you come to February, March, and you look at the size of the squads, City have got a bigger squad if people lose form, people get injured".More news: Gaza: Israeli Snipers Kill 2 Protesters, Including Child