Real Madrid star Kaka risked his career by playing for Brazil at the World Cup, according to the doctor who performed an operation to repair a meniscus injury in his knee this week.
Kaka underwent surgery after complaining of pain at the club's pre-season training camp in Los Angeles and a routine medical check revealed the player would need arthroscopic surgery.
The doctor who performed the surgery, Marc Martens, knew straight away the injury was serious and claims that he pushed himself too hard in South Africa.
''As soon as I saw him I could tell it was serious,'' the specialist told Marca. ''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.''
Martens claims the injury could have spelt the end for Kaka as a professional footballer, as opposed to the three to four months he will now sit out.
''It could have finished his career because it's a very serious injury - it could have destroyed him,'' he said. ''But thank God he has had the operation at the crucial moment and everything has turned out wonderfully.''