For Sarri, it was the heaviest defeat of his coaching career and raised questions over his future.
Chelsea's next fixture is against Malmo in the Europa League on Thursday.
Eden Hazard went to sleep from Kevin de Bruyne's quickly taken free-kick and Bernardo Silva had acres of space to cross for the England global to fire home.
While it appears to have been an honest mistake, it could have quite easily be misconstrued as a disrespectful act by Pep Guardiola's side.
Guardiola fell to the floor in exasperation when Aguero somehow side-footed wide with his easiest chance of the game moments later.
But he need not have anxious that would prove a costly miss as the Argentine made amends in stunning fashion by blasting into the top corner from 25 yards to double City's after just 13 minutes.
AGUERO would go on and redeem himself with a goal of the season candidate.
"It doesn't happen to Chelsea much, so when it does, it's a shock".
Chelsea looked powerless to stop the onslaught and Harris believes there is a void in the dressing room that needs filling before they can start to recover.
Chelsea, on the other hand, have plenty to think about as they try and challenge for the top four.
But, speaking to the press afterwards, as quoted by the Evening Standard, the 60-year-old was unbending in his belief in his style of play, though was bullish in admitting the current footballing fare was not close to his enduring philosophy.
This gritty success was the ideal preparation for hosting Borussia Dortmund in the Champions League last 16 first leg on Wednesday. I just said to them thank you for what they have done. "In my first year, we could not play in the way I wanted". Five games in the space of 14 days is elite.
A key turning point came on the hour when Jamie Vardy missed a penalty for Leicester with his first touch of the game.
"If the president [Roman Abramovich] calls, I'll be happy, seeing as I never hear from him".
Despite all the accolades, the Argentinian claims all that really matters is winning trophies and this emphatic victory took quadruple-chasing City back to the top of the Premier League. "We did it, it's an incredible compliment to the players, they are outstanding", added the Spaniard.