Sir Alex Ferguson: An honour to face him says Robert Mancini
Manchester City manager Roberto Mancini says it has been "a great honour and pleasure" to take on Manchester United manager Sir Alex Ferguson.
Ferguson, 71, after 26 years in charge and will be replaced by David Moyes.
Mancini said: "It was a great honour to beat him at Old Trafford and I wish him good luck for his future.
"I don't think there'll be another manager like him. To win every trophy for 27 years is incredible situation."
Mancini got the better of Ferguson to win the Premier League title last season - including a famous 6-1 win at Old Trafford in 2011 - but saw Ferguson respond with a dominant title win this season.
And Mancini expects United to remain a force under Moyes next season when he after leaving Everton after 11 years in charge.
"In Europe, there are other good managers. I don't know if you can say Sir Alex is the best ever but he is the best in the last 27 years," Mancini said.
"A top club, a big club like United, you can change the manager. Sir Alex built this team but it is a big club with a big history and I don't think it will change something."
One of Ferguson's biggest rivals in the past 20 years has been Arsenal boss Arsene Wenger, who called the United manager's reign "immaculate".
"It is difficult to imagine English football without him, but it's now a reality and a fact," Wenger added.
QPR boss Harry Redknapp says Ferguson "will be a great loss to English football".
Redknapp said: "Sir Alex has had a massive influence on so many managers. He's achieved so much.
"Davey is a great boy, a top manager. It's good that a British coach has got the top job."
West Ham manager Sam Allardyce called Moyes "the perfect candidate" for the United job and anticipated an emotional atmosphere when he takes the Hammers to Goodison Park on Sunday for Moyes' final home game in charge.
"I hope their crowd show their appreciation for him. You can't do anything but applaud him for what he's done in 11 years at Everton," Allardyce said.
"He'll face the challenge head on. It's one of the biggest jobs in club football."
Stoke manager Tony Pulis believes the appointment of Moyes is a positive for young British managers in the game.
He said: "David Moyes has come from bottom to the top, and for him to have this chance is brilliant. It's great for all young, aspiring managers, because it shows that young British managers are given a chance at the very top."
Moyes has yet to win a major trophy but current Manchester United captain Nemanja Vidic believes the new boss can continue the club's success.
"I'm looking forward to working with David and I believe I will have the same success I had with Sir Alex," Vidic told the club's official website.
"David and Sir Alex share some similarities - they are very passionate, they are both winners and you can see the way they approach the games and how they run things."