MADRID, Jan 14 (Reuters) - Barcelona's Brazilian midfielder Thiago Motta will be out for about six weeks after injuring his right knee during training, the Primera Liga club said on Saturday.
Motta will undergo arthroscopic surgery next week to repair the damage the club's medical services reported.
The 23-year-old missed most of last season with a serious knee injury.
His absence is a blow to coach Frank Rijkaard who has already lost Spain midfielder Xavi to a knee ligament injury.
Cameroon striker Samuel Eto'o leaves to join up with his national squad for up to a month at the African Nations Cup in Egypt, after Sunday's league match at home to Athletic Bilbao.
Barcelona top the Primera Liga by four points from second-placed Osasuna.