MADRID, Spain — Five-time major champion Seve Ballesteros suffered a complication following surgery on a brain tumor, but is in stable condition, Madrid's La Paz hospital said Thursday.

Doctors removed a piece of Ballesteros' skull to relieve pressure that was building up on the brain following Tuesday's surgery. The hospital said in a statement that the 51-year-old former golf star is stable but still in intensive care.

On Tuesday, doctors removed a sizable part of Ballesteros' tumor. It was not immediately known if it was malignant.

The hospital said Ballesteros had presented a "decreased level of consciousness by brain swelling," adding that a decompressive craniotomy had been carried out.

Decompressive craniotomy involves part of the skull being removed to allow a swelling brain room to expand. Doctors say it is not uncommon after such operations.

Ballesteros, who won three British Opens and two Masters, briefly lost consciousness and on Oct. 6 was admitted to the hospital, where the tumor was discovered. On Sunday, he acknowledged having a tumor and said he faced the "hardest challenge of my life."

Ballesteros, who won a record 50 tournaments on the European tour, retired last year because of a long history of back pain and has since concentrated on golf course design.

Ballesteros transformed European golf. After the Ryder Cup was expanded to include continental Europe in 1979, Ballesteros helped beat the United States in 1985 to begin two decades of dominance. He also captained Europe to victory in 1997 at Valderrama, Spain.

Ballesteros and Jose Maria Olazabal made one of the most formidable partnerships in Ryder Cup history, with 11 wins, two losses and two halves.