RIO DE JANEIRO, Brazil — Kaka had arthroscopic knee surgery today and will miss Brazil's upcoming exhibition tour to the United States.

The surgery lasted 50 minutes and was performed by Dr. Jose Luiz Runco, the head physician of the Brazilian national soccer team, Eliane Belleza of the Pasteur Hospital said. Kaka, the reigning FIFA World Player of the Year, is expected to leave the hospital Friday.

The 26-year-old, who stars for AC Milan in the Italian League, will miss matches against Canada at Seattle on May 31 and Venezuela at Foxborough, Mass., on June 6. Kaka hopes to return for World Cup qualifiers against Paraguay on June 15 and Argentina on June 18.

"Dr. Runco didn't set any timeframe," Belleza said. "It varies from player to player. We have to wait and see."

In addition, injured defender Alex was replaced on Brazil's roster by Henrique for the exhibition games and by Thiago Silva for the World Cup qualifiers.