Crespo played under the Portuguese in Chelsea before the pair reunited at Internazionale.
"It was more than just about me. It was amazing, his history in Inter," Crespo told Goal.comahead of the Chelsea legends game against Inter Forever on Friday .
"I tried to help him when he moved there. It was great for us to work together again after Chelsea.
"Jose is different. Jose makes a difference and writes history because the future of his clubs will never be the same after him, because when he comes he brings a warpath as a manager. I think he became a great manager after he left Porto. I think Chelsea gave him more of a reputation which grew and grew."
The Argentinian legend thinks Mourinho is more than the usual manager and that he has changed the football clubs all-around.
"I think to be part of that moment was like being part of history. After Mourinho, football managers all changed. They changed what they said in press conferences and the way they behaved. Everything changed. In that moment we understood that managers don't just choose the starting 11.
"They must understand everything all around. It is about your relationships with your players, staff, doctors and media. He understood all of it and he was very clear with everybody. With the fans, with the media, the players and the owners. I understood that it is more than just about the first XI, he was more than that."