City owner Sheikh Mansour and chairman Khaldoon al-Mubarak had become increasingly convinced that Hughes was not the man to steer the club into the top four despite a summer transfer outlay of £120 million.
Nevertheless, Hughes was axed with the club sitting in sixth place in the Premier League table – a position the owners had previously indicated would be an adequate return for the campaign.
Speculation had been mounting that Hughes was set to be replaced by Mancini, and City's senior players were informed of the decision minutes after an entertaining 4-3 win over Sunderland.
The appearance of Mancini at Eastlands had fuelled suggestions that Hughes' 18-month reign was about to come to an end, and he seemed resigned to his fate as he watched Roque Santa Cruz seal three points against the Black Cats.
The 45-year-old Mancini guided Inter Milan to three successive Serie A titles from 2006, and Khaldoon said in a statement: "Roberto is a hugely experienced manager with a proven track record of winning trophies and championships."
With Brian Kidd as his number two, Mancini would ultimately enhance his reputation by leading City to a dramatic Premier League title win in 2012, after a dramatic final-day win over Queen's Park Rangers.
He signed a new five-year deal in July 2012, but the club owners were growing increasingly restless and Mancini was dismissed in May the following year, three years after a shock FA Cup final defeat to Wigan.