"I'm very sad, it's part of my history that's gone," the coach declared in the press conference.
Mourinho, who won the European Championship with the Dragons in 2004, sent his condolences to the family and offered words of comfort to his children, highlighting the leadership qualities of the former defender, who has died at the age of 53.
"Jorge was one of those guys who, as I say, cleaned up the mess and let the coach work as a coach. (...) Sometimes, it's not about the armband," he declared.
The Portuguese coach won national and European titles, as well as the UEFA Cup, alongside Jorge Costa, one of the cornerstones of the defense with which he dominated while playing for the Blue and Whites, launching a career filled with titles in several countries.
"If he could talk to me now, he would tell me to go to the press conference, talk, and play the game. That was Jorge. (...) I'll cry later," said Mourinho, visibly emotional.
On Instagram, the coach echoed the same sentiment, declaring that Costa would ask him to be "prepared and strong" for the players he now manages at the Turkish runner-up.
"I promise you, 'Bicho,' I will do this. Rest in peace, because your legacy lives on with us," he wrote.
The former FC Porto player, and until now the director of professional football for the Dragons, died on 5 August at the age of 53, following cardiac arrest.
A source at São João Hospital told Lusa that Jorge Costa "went into cardiac arrest in the emergency room" of that hospital, where he was transported, after feeling unwell at the club's training center in Olival, Vila Nova de Gaia.
Jorge Costa represented the Dragons in 383 official matches between 1992 and 2005, and captained the club for several seasons, winning a Champions League, a UEFA Cup, an Intercontinental Cup, eight national championship titles, five Portuguese Cups, and five Super Cups.
He was capped 50 times by the Portuguese national team, also winning the 1991 U-20 World Cup.