Deco played for Mourinho at Porto.
"He was a great coach, but above all that, a friend off the pitch," Deco told the Daily Mail. "I think he has changed as a coach, because it's a different game now.
"He's taught me many, many things. When he came to Porto he brought a new mentality. Many players didn't believe it was possible to win the Champions League.
"I'll never forget that.
"We had a good team but his narrow-mindedness showed us how to do well and win the big games."