Seve Ballesteros will undergo a third operation tomorrow to ease the swelling on his brain although hospital authorities insist he remains in a "stable condition".
The 51-year-old five-time major winner has had two operations on his brain since the diagnosis of a tumour earlier this month and is being kept under sedation at the Hospital Universitario La Paz in Madrid.
Ballesteros' condition was reported to be improving on Wednesday but doctors have now decided to operate on him again.
A hospital statement read: "Ballesteros will undergo a new operation on Friday. He continues to be in a stable condition within the seriousness of his condition.
"In the operation they will work on the edema and the intracerebral haematoma that has developed in the past few hours and they will increase the removal of the remains of the tumour.
"The tumour has been classified as an oligoastrocytoma (which affects the cells which cover and protect the nervous system cells in the brain and the spinal cord) and is located in a very deep area which makes it very complicated to reach."