Motherwell midfielder Phil O'Donnell died from heart failure, the club said yesterday after a post-mortem.
The 35-year-old former Celtic player collapsed on the pitch during the Scottish Premier League match against Dundee United on Saturday and was pronounced dead at hospital having failed to regain consciousness.
"The post-mortem revealed that Phil had suffered left ventricular failure of the heart," Motherwell club doctor Robert Liddle said.
Several matches in Scotland have been postponed today as a mark of respect for O'Donnell, including Motherwell's away game at Hibernian and the Old Firm match between Celtic and Rangers.
Tributes were also paid to O'Donnell before yesterday's Premier League matches in England.
O'Donnell's funeral service will take place in Hamilton on Friday at noon.
Meanwhile, O'Donnell's widow has spoken publicly for the first time since his death on the field.
"Although he achieved so much in football the most important thing for him was his family," she said.
"He would like to be remembered as a family man and we were all so proud of him."