By FOX Sports Staff
Back then, the Portuguese was in charge of Porto and saw his side matched up with the Red Devils in the last-16 stage of the Champions League.
Porto managed to defeat United 2-1 at the Estádio do Dragão and drew the return leg 1-1 to eliminate Ferguson's side from the competition.
Mourinho went on to win the UEFA Champions League that season and was subsequently hired at Chelsea where he shared a respectful rivalry with the same man.
Nearly ten years on since that first encounter, Mourinho told the Offside Rule podcast of exactly how the two began their friendship.
"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," Mourinho remarked of the game that first pitted two of the most famous managers in European football history.
"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."
With just two days left until Ferguson calls it a day at the Old Trafford helm, Mourinho also took the opportunity to explain that he would miss the 71-year-old. He also commended United for having the faith in Ferguson through thick and thin over the past 26 years.
"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.
"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 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."
The duo last faced one another in this year's Champions League round of 16 stage with Mourinho emerging the victor once more over the two-legged contest.