Sir Alex Ferguson has criticised Manchester City for sacking Roberto Mancini, branding it "amazing" that they fired a manager with his track record.
The Italian was dismissed on Monday, 48 hours after losing the FA Cup final and on the first anniversary of the day City became champions for the first time in 44 years.
And Ferguson expressed sympathy for Mancini, who inflicted the heaviest defeat of his managerial career when City won 6-1 at Old Trafford in October 2011.
"It is quite amazing," said the Manchester United manager. "He has won the FA Cup, been in the final, second in the league and won the league and it's not good enough?
"I was surprised, but actually no, you can't say you are surprised not with some owners today. You can't be surprised, but I still don't think it was right."
Ferguson, whose 26-year- reign at United ends when he retires after Sunday's trip to West Bromwich Albion, has long argued that managers need time and believes too few are being shown patience.
He explained: "I was with the chief executive of Liverpool at our reserve game the other night and he told me that Brendan Rodgers, who has not been in the job a year, is the 30th longest-serving manager in the country. That's incredible."
Ferguson will be replaced at Old Trafford by David Moyes, who has managed Everton for the past 11 years, and the 71-year-old believes United will have more stability than their local rivals.
"What happens at Man City won't have any bearing on David," he added.
"He's got the structure here and he's got the experience. He's had to handle things at Everton that are more difficult probably. I don't think that matters.
"I think the enormity of the club will be the most difficult aspect, he will soon realise that anyway. The global brand and number of sponsors we have, he has to fit into that. I don't think that's an issue though and the most important thing is the team.
"He's got a good squad of players and he will want to add to that. He will have his own ideas and that's good. He will be fine."