Real's official site stated that the Brazilian, who left the pre-season camp in the US for Belgium, performed an arthroscopic operation in Antwerp.

Meanwhile, Real boss Jose Mourinho praised his star playmaker, but didn't seem to be overwhelmed by the blow.

"He’s a very popular player among his team mates and also a very good player but we want him at 100 percent so that he is happy," Mourinho told a news conference in San Francisco.

"If we have to lose him for a while it won’t be a drama. We have other players and that’s that."