Bobby Robson will undergo surgery to remove a brain tumour this week.
The former England and Newcastle United manager, 73, fell ill during a match at Ipswich, the club he managed for 13 years and who have now made him president, a fortnight ago.
It was initially thought that Robson had suffered a stroke but doctors have discovered a tumour.
Robson, who has overcome cancer three times in the past, told the Mail On Sunday: 'I had a scan to assess why I felt unwell and had to leave the game at Ipswich early, and the doctors discovered a small, operable tumour that caused an affliction on the left side of my face.
'On Wednesday I will have an operation to remove the tumour and, as surgeons tell me the rest of my body is clean, I should be able to make a full recovery.
'The tumour is in my brain, which sounds bad, but it is in a position where it can be removed relatively easily and it's extremely small - the size of a grape - which indicates they have caught it early.'
Robson, currently an international consultant for the Republic of Ireland, took England to the semi-finals of the 1990 World Cup.
He went on to manage with great success across Europe, before ending his club career at Newcastle.
