Real Madrid star Kaka underwent arthroscopic knee surgery in Los Angeles after complaining of pain during the preseason camp and the doctor who performed the surgery said Kaka had risked his career by playing for Brazil at the World Cup.

"As soon as I saw him I could tell it was serious," Dr. Marc Martens said. "His career has come under serious danger. He started playing with some niggling injuries and ended up with unbearable pains. I understand that it's a unique competition and that there was pressure, but he pushed himself much too hard against Holland and Chile. He admitted he was in a lot of pain.'"

Kaka, who missed much of Real Madrid's last season injured, will be sidelined for three to four months.

''It could have finished his career because it's a very serious injury - it could have destroyed him,'' Martens said. "But thank God he has had the operation at the crucial moment and everything has turned out wonderfully."