Jose Mourinho has admitted he will miss his duels with Sir Alex Ferguson after the Scot announced his decision to retire from the game at the end of the season.
The Manchester United boss will call time on his managerial career after his final game against West Brom on Sunday, bringing to an end a 26-year career in charge at Old Trafford.
Mourinho, expected to return to the Premier League in the summer - proved to be one of his toughest opponents after he became Chelsea boss in 2004.
The Real Madrid coach admitted he will miss locking horns with Ferguson when his next side, whoever that may be, line up against Manchester United.
"We will all miss him and for me it will be difficult to go to Old Trafford, especially for the first time, to play against Manchester United without such a figure in the opposite dugout," Mourinho told The Offside Rule podcast.
Asked why Ferguson will be missed so much, Mourinho said: "He is unique and probably Manchester United are a unique club because they gave the manager the conditions to do the job he did.
"Everybody knows that the beginning was not easy for him. Everybody knows that it took him three or four years to win the first piece of silverware and Man United gave him the conditions to do an incredible job. After that he was unique, absolutely unique.
"The number of trophies he won for Manchester United in English football is absolutely amazing and to manage for more than 20 years is incredible."
Mourinho first came to the attention of Ferguson when the Special One's Porto side dumped the Red Devils out of the Champions League in 2004.
The pair's last meeting came earlier this season when Mourinho got the better of his friend once more, overseeing Real Madrid's controversial win against United in the last-16 of the Champions League.
When quizzed about what his favourite meeting with Ferguson was, Mourinho replied: "If I had to choose, I would choose the first one. It was 2004. It was in fact my first match as a manager on English soil. It was Manchester United against Porto in the Champions League.
"We scored in the last minute and we went through and it was not normal for me, not normal in the culture that I knew, that the opposition manager knocked on our dressing room door after the match - which was a moment when he would be very, very disappointed - and came in to congratulate me and invite me to go to his room for a glass of wine.
"That marked our relationship. After that we played so many times with each other and the next year I moved to England with Chelsea. After that the relationship went in that direction - it didn't matter who won and who lost. The respect was always there."