Brazil [Images] and AC Milan playmaker Kaka [Images] underwent surgery on his left knee on Friday and is doubtful for next month's World Cup qualifiers against Paraguay and Argentina.

Brazil team doctor Jose Luis Runco said the arthroscopy operation had gone well but did not want to estimate how long the World Player of the Year would be out of action.

"The result was very positive but I don't want to make a prediction," Runco told reporters. "The certainty is that he's out of the friendlies. We'll think about the World Cup qualifiers later."

"We'll have a look every day. We're not going to jump the gun so that he can play for the national team."

Brazil face Canada [Images] in a friendly on May 31 and Venezuela on June 6, both in the United States.

They are away to Paraguay in a World Cup qualifier on June 15 and at home to Argentina three days later.

Runco said Kaka had suffered damage to the meniscus caused by overuse. "It's like having a stone in your shoe," he said.

On arriving at the Rio de Janeiro hospital for the operation, Kaka told reporters: "We've done everything possible to avoid surgery but there's no way out.

"My thinking is that I will miss the friendlies but will be ready for the World Cup qualifiers."

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