And he shared a rocky rapport with the Manchester United boss – that started during his time with FC Porto when Ferguson refused to shake his hand – but the man who is tipped to take over the Old Trafford hotseat is insisting they always maintain a healthy friendship.
"He's unique," said Mourinho. "Especially in the modern day.
"If you go back many years, then you will find somebody like him but [it's amazing] in the modern day at the highest level, where it is really difficult to survive in our job.
"He's absolutely incredible at what he does and we can't even imagine when he'll stop. He's unbelievable."
Mourinho’s men will line-up against Premier League leaders Manchester City – who finished 16th when the Portugal boss’ delivered the title in his first season with Chelsea – in the Champions League tonight.
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