Jorge Costa, who was the leader of the Porto team from Jose Mourinho to the Champions League, died at the age of 53.
According to reports in Portgual, Costa had a cardiac arrest during the Porto training camp at the Olival Stadium on Tuesday.
Costa, who had had a heart attack earlier in 2022, reportedly complained several times about intense heat after giving a television interview to SportTV.
A Bola reported that the medical team of Porto offered first aid and used a defibrillator before Costa was brought to the Sao Joao hospital.
Costa was admitted to Intensive Care, but died in the early afternoon.
The former central defender played for Porto between 1990 and 2005 and made 324 performances in all matches for the club.
He is best remembered for serving as Captain of Mourinho when Porto won the Champions League famous in 2004.
Porto had defeated Manchester United, Lyon and Deportivo La Coruna in the knockout phase of the competition before he had broken down a 3-0 win over Monaco in the final.
Costa had also lifted the UEFA Cup last season and won the Portuguese title with the club eight times.
He also won the Intercontinental Cup, five Taca de Portugal trophies and eight super cups during his time in Porto.
Mourinho had praised Costa in 2022 as a 'leader' of his team and remembered a story in which the center Back had to do the 'dirty work' to express their manager's anger in half time in a match they had left 2-0.
He stated that Costa then asked him 'Coach' before the defender rare two goals scored to help secure a 3-2 victory.
Costa returned to the Porto last year to serve as director of Voetbal.
“Jorge Costa, the legendary FC Porto captain and current director of professional football, died of cardiac arrest this Tuesday,” said a Porto statement.
'Fútbol Clube do Porto expresses his deepest sorrow and consternation at the death of an inescapable figure in the history of the club.
'Throughout his life, both on and outside the field, Jorge Costa embodied the values that FC Porto defines: dedication, leadership, passion and a relentless spirit of performance. He touched generations of fans and became an important symbol of Porto.
'In this time of immense sorrow, Futebol Clube do Porto is expanding its deepest condolences to the family of Jorge Costa, his friends and everyone who shared unforgettable moments with him.
'Because this is a time of sorrow for his entire family and for the Porto Alegre family, we ask everyone to exercise the required discretion and respect in this time of farewell. More information will be released in due course.
'Jorge Costa's Legacy will forever live on in the memories of all Porto fans.
“You will never be forgotten, captain.”
The defender made 50 international performances for Portugal, including representing his nation at the 2002 World Cup.
Costa had a short spell in the Premier League and made 24 performances in a loan saying with Charlton in the 2001-02 season.
He ended his gaming career in Belgium with Standard Liège, before he started a management career with him to take the lead over 17 different teams.
This included coaching eight different Portuguese teams, including Braga, as well as spells in Cyprus, Romania, France, Tunisia, India and as head coach of the national team of Gabon.
A Braga -Teston was: 'SC Braga with deep sorrow received the news of the death of Jorge Costa, a historical figure in national football who also represented the colors of our club during his extensive sports career, both as head coach as an assistant coach.
“The terrible news of his passing shakes the entire national sports community, and SC Braga can only participate in the enormous pain that his family, his friends and the entire FC Porto structure have shared.”
Charlton also paid a tribute to writing in a statement: 'We are deeply sad to learn about the death of the former player Jorge Costa at the age of 53.
“The thoughts of everyone at Charlton Athletic are with Jorge's family and friends in this difficult time.”
Cristiano Ronaldo also shared a message on Instagram, writing 'Goodbye, Jorge Costa'