The 46-year-old former midfielder recalled how “different” his ex-boss’ approach was when he first arrived at Porto and he found him to be “way ahead of [his] time”.
Asked about his first impressions of Mourinho, Deco told FourFourTwo magazine: “That I was seeing a completely revolutionary manager, in terms of training and the way he looked at games.
“It was just different to everything that was being done at the time.
“Mourinho used to organize every training session in an impressive way, always linked to the next opponent, who he had always studied in depth.
“It was way ahead of its time.”
Deco was “incredulous” at how well Mourinho could envisage the side’s games because he poured so much into studying their opponents.
The former Portugal international - who also played for the likes of Chelsea and Barcelona - said: “The most incredible thing was his ability to predict what would happen in matches. It always happened!
“He would say how the match was going to go, then it would happen and I was incredulous. How did this guy know?
“Today, it’s much easier to study rivals, with the tools we have available.
“Back then, it wan’t always like that."
Deco was always amazed by Mourinho's level of detail and planning.
Deco said: “He was always able to dissect the characteristics of the opposing team and show us the way to beat them.”