Ex-Man City managers Keegan, Royle: Mancini on hiding to nothing
The pair claimed the club acted too hastily in dismissing Mark Hughes, who paid the price for a run of two wins in 11 games.
Royle, who managed City from 1998 to 2001, said on ESPN: "They had a big game with Manchester United to come, they just beaten Chelsea, prior to last week had only lost one game in the 94th minute at Old Trafford.
"You don't change from an indifferent side to a totally winning side overnight. And I thought, okay it stalled a little bit, that at least you could see progress."
Royle added: "You wonder how many of the players Mark Hughes has bought he (Mancini) fancies. Does there have to be another wholesale change?"
Wednesday's three-goal hammering at Tottenham convinced owner Sheikh Mansour. Keegan, City boss between 2001 and 2005, felt the club's owners wanted to appoint their own manager.
"He wasn't appointed by these people and that's the big problem," he said.
"They want their own man in.
"When you read the statement it's not that of a real football club, it's that of a business.
"Although it's very cold and clinical and business like, for me, not enough time for this man to even stamp any sort of authority on this club."
Royle claimed there would be little room for error for Mancini.
He said: "He's got to do very, very well, that's for sure.
"Mark Hughes has lost two games this season and he's out. So Mancini's got a tall order."
The former Sampdoria forward won three Serie A titles in his time in charge Inter, but Keegan pointed out he has no experience of managing in the Premier League.
"I think they've gone for the very, very best," he said.
"The thing is he doesn't know the Premiership. There are no Italian players at the club."
But he added: "In Mancini, there's no doubt about it they've got an absolutely top, top notch manager."
Asked what Mancini would have to achieve this season, Keegan joked: "Win the Premiership, win the Carling Cup, win the FA Cup and you might keep your job."