(CNN) -- Spanish golf legend Seve Ballesteros had a fourth and "scheduled" brain operation at Madrid's La Paz hospital on Tuesday as he battles back from a malignant tumor.
Seve, who won a record 50 tournaments on the European Tour, is facing the "hardest challenge of my life."
The five-time major champion is said to be stable and back recovering in ICU after the latest surgery to help drain fluid from the brain.
"The patient Severiano Ballesteros underwent scheduled surgery for the placement of a cephalorachidian fluid VP shunt," said the hospital in a statement.
"In the same intervention the medical team has done a cranioplastia to repair a bone defect. His situation is stable and he will remain in the Intensive Care Unit."
Improving Ballesteros was moved out of intensive care two weeks ago, but doctors warned that the healing process was slow and there was no timetable for his release.
The Spaniard, who won three British Opens and two Masters titles, was admtted to hospital after he briefly lost consciousness while at Madrid's international airport on October 5.
He underwent a first operation on October 14, when a sizable part of the tumor was taken out.
In a second operation, on October 16, a part of his skull was removed -- a procedure known as decompressive craniotomy -- to allow room for a swelling brain to expand.
Ballesteros then underwent an intricate six and a half hour operation on October 24 to remove what remained of the tumor and reduce the swelling.
Seve, who won a record 50 tournaments on the European Tour, has called the situation the "hardest challenge of my life."
He retired in 2007 following a long history of back pain and has since concentrated on golf course design.
A three-times British Open and twice Masters champion, Ballesteros is often praised for having transformed European golf.
He helped beat the United States in the 1985 Ryder Cup to begin two decades of dominance and also captained Europe to victory in 1997 at Valderrama in Spain