Cameroon captain Samuel Eto'o remains a serious doubt for Monday's World Cup Group A clash with Brazil in Brasilia as he continues to struggle with a knee injury.

Eto'o, 33, played no part in training with the rest of the Cameroon squad at the National Stadium, at least not the first 15 minutes that were open to the press, preferring instead to chat with members of the Cameroonian police who are accompanying the squad and watch on from the dugout.

The striker injured his right knee in the Indomitable Lions' 1-0 defeat to Mexico in Natal on June 13 and has not trained since, playing no part in the 4-0 loss to Croatia in Manaus last Wednesday.

That result ended Cameroon's chances of qualifying for the knockout stages of a World Cup for the first time since 1990, leaving them with only pride to play for against the tournament hosts.