Brazil doctor Rodrigo Lasmar says the defender will be out for at least three months after getting hurt Sunday in Poland, where the team will play Japan in an exhibition Tuesday.
Lasmar says Marcelo's injury may require surgery. The player will return to Spain on Monday to be evaluated by Real Madrid doctors.
Marcelo says he will ''be back soon'' and that he wants to fully recover in time for the 2013 Confederations Cup that Brazil will host.
Marcelo has been Brazil's starter at left back under coach Mano Menezes, who will not replace him on the squad before Tuesday's match.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO Sports and on Facebook at AhramOnlineSports)