Phil O'Donnell, the Scottish footballer who collapsed during a match on Saturday, died from heart failure, his club, Motherwell, said last night.
The result of a postmortem on the 35-year-old father of four was revealed after his widow, Eileen, spoke publicly for the first time about his death while leading his side against Dundee United.
She visited the makeshift tribute created by fans with scarves, strips and pictures at the club's Fir Park ground, saying: "Although he achieved so much in football, the most important thing for him was his family. He would like to be remembered as a family man and we were all so proud of him. We are all devastated by what has happened."
She said the family had been overwhelmed by messages of support.
Dr Robert Liddle, the club doctor, said: "The postmortem revealed that Phil had suffered a left ventricular failure of the heart."
The funeral will take place at St Mary's Church, Hamilton, on Friday, the club said.
O'Donnell, who also played for Celtic and Sheffield Wednesday, died as he was being substituted during his side's 5-3 victory, the latest of a list of footballers around the world to die while playing or training, a trend that could lead to further reviews of how players are tested and monitored.
The Celtic and Scotland defender Gary Caldwell has called for investigations into the potential side-effects of food supplements and energy drinks after the death of O'Donnell.
Caldwell is concerned about the increasing number of footballers dying young. The Cameroon midfielder Marc-Vivien Foe (28), Benfica's Miklos Feher (24) and Sevilla's Antonio Puerta (22) are recent football fatalities and the Republic of Ireland international Clive Clarke (27), on loan at Leicester, survived two heart failures in an English League Cup match in August.
"You drink energy drinks, you take supplements and you do it to become a better player," said Caldwell. "But I think somebody has got to look into it and try to see if it does affect you. Sometimes the fitter you are means you are a time-bomb waiting to happen.
"I think something should be done, a study on supplements and energy drinks and stuff that people take to try and improve and get the best out of themselves. I don't know if things like that are involved but I don't think it can be a coincidence."
Caldwell added British authorities should follow the lead of the United States, where studies have been conducted after the deaths of NFL players.
The Old Firm meeting with Rangers today was postponed at Celtic's request because some of their players were still in shock. Caldwell added: "I don't think that at any point in my life I thought football was as insignificant as I did on Saturday night."
The player's father, Bernard, has said the family were struggling to come to terms with what had happened.
"None of us can yet comprehend what has happened," he said in a statement read on his behalf outside Fir Park. "But we are overwhelmed by the support and messages from people inside and outside the football world."
Celtic manager Gordon Strachan and Rangers captain Barry Ferguson were among the figures from across the world of football who visited Fir Park to see the tributes.
Motherwell's match at Hibernian and Gretna versus St Mirren at Fir Park, scheduled for today, have also been postponed as a mark of respect.
Representatives of other football clubs and organisations are expected to join family, friends and Motherwell FC players, staff and officials at the noon funeral service on Friday.
