Marcelo, who left early in the group stage finale against Serbia because of back spasms, is still uncertain for the match against Mexico.
Brazil collected seven points from their three group matches at this summer's competition. The Real Madrid defender was replaced with Filipe Luis and the Atletico Madrid defender is expected to retain the starting spot when the Selecao face Mexico in the second round.
And now Dr Rodrigo Lasmar has revealed that the problems to Marcelo may have come as a result of a hotel mattress. "Maybe it was the hotel's mattress, which was a bit more soft than usual. We are optimistic he can be used in the game", Lasmar said. But [the injury] happened because he made a rotation movement and felt uncomfortable after.
Marcelo has missed games for Real Madrid due to muscle problems in both of the last two seasons.
Marcelo's exit marks the latest in a Brazil side beset by injuries for this World Cup. Soon I will be back!
Goal: Titus declared the basis of Brazil for Mexico - without Marcelo and CoutinhoHead coach of Brazil Tite said who will play in the 1/8 finals of the world championship against the team of Mexico.
Juventus winger Costa is recovering well, said Lasmar, but will not be fit for Monday's match in Samara.