Manchester City manager Roberto Mancini says it has been an honour to compete against Sir Alex Ferguson over the past three years.
Mancini's arrival at the Etihad Stadium in December 2009 has coincided with a resurgence in the rivalry between City and Ferguson's Manchester United at the top of the Premier League. City memorably beat United in the 2011 FA Cup semi-finals and then pipped them to the Premier League title in dramatic circumstances last year, a season in which they also soundly defeated their neighbours 6-1 at Old Trafford.
United have reasserted themselves by reclaiming their league crown in emphatic fashion this season, an achievement which has proved Ferguson's final act as United boss with the Scot now stepping down after more than 26 successful years.
Mancini said: "For me, it has been a great honour and pleasure to compete against Sir Alex for three years. It was a great honour to beat him in Old Trafford and I wish him good luck for his future.
"Everyone can have his opinion but one manager who stays for 27 years in the same club and won every trophy for 27 years - it is an incredible situation.
"I don't think there will be another manager like him. It is difficult to say Sir Alex is the best (ever) but he is the best in the last 27 years."
Ferguson's retirement will leave a big hole for his replacement David Moyes, the current Everton boss, to fill but Mancini knows he cannot expect the balance of power to shift back in City's favour.
The Italian added: "I don't think this. At 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."