"Cameroon have beaten Brazil before, yes. So it's not completely out there," Song said.
"I have put all my efforts and energy into finding solutions to a situation that a footballer often experiences, but there has been no will on the other side. Some moments are difficult to assimilate."
But a loss for either team -- combined with a draw between Brazil and Switzerland -- would prematurely bring the curtains down on their campaign, with nothing to play for but pride in their final group game on December 2.
"If you look at our team, only three players of the 26 have played at a World Cup before. This is a new generation of players. There is everything still left to play for. We have not lost hope."
The Switzerland goal came after Cameroon had dominated the first half, missing several good chances to take the lead.
With both Serbia and Cameroon desperate for points after their opening defeats, they played out one of the most entertaining games of the tournament
Senior Cameroon players have asked coach Paul Le Guen to reconsider his team selection for their second World Cup match against Denmark because he has included too many youngsters.
Cameroon, finalists in 2008, came back from the brink of elimination to scrape past Zambia 3-2 and revive their African Nations Cup campaign on Sunday.
Cameroon are confident to set an African record sixth World Cup finals appearance in Germany next year.
Cameroon captain Rigobert Song said on Friday he still could not believe what had happened to his great friend "Marco".
The Cameroon captain's header gave his country a 2-1 win over Benin in their World Cup qualifying match.