Kaka has pledged to once again be the best player in the world, saying the doctor who operated on his knee exaggerated the seriousness of his injury.

After a routine pre-season check by Madrid doctors discovered a problem, Dr. Marc Martens performed arthroscopic surgery on Kaka's left knee on Aug. 5 then claimed the player put his career in jeopardy by playing at the World Cup.

But Kaka denied that in an interview published by Spanish newspaper Marca on Friday.

"Martens is a great professional but he raised the alarm, he exaggerated a lot," said Kaka.

Martens said Kaka was in unbearable pain during Brazil's quarter-final loss to the Netherlands in the World Cup.

Kaka said he played in pain before that game.

"I played in pain in a lot of games, not just with the national team, but also with Real Madrid," he said. "And not just my knee, but other parts of my body, too."

After a 65 million euro (C$86 million) move from AC Milan, Kaka had a disappointing first year at Real Madrid last season, when he was hampered by a groin injury. The groin problem aggravated the knee injury, he said.

He said he got through the pressure caused by the injury with the help of "faith, family and friends," and he expects to return to action in four months.

"I will be the best in the world again. Today it's difficult to say this, but I think I'm going to be successful with Real Madrid," he said. "I had the operation to be No. 1 again."