The 33-year-old played in his side's 1-0 defeat to Mexico in their Group A opener on Friday but has failed to take any part in training since that game.
After admitting that a knee problem flared up as early as the ninth minute of that game, the former Barcelona striker hopes for some divine intervention.
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"If this is not the case, I will always play my role as captain and especially as the big brother to push my young team-mates to victory."
Eto'o may miss the rest of the group stage after revealing that the injury had bothered him for a long time.
"For three and a half months, I have not had the time to recover," he explained. "You could see that even in the build-up to the World Cup; I hadn't had a lot of practice until the friendly against Germany."
After their loss to Mexico, Cameroon head into Wednesday's clash with Croatia seeking to keep their qualification hopes alive before they take on tournament hosts Brazil in their final group match on June 23.
Cameroon coach Volker Finke had already confirmed that Eto'o failed to train over the weekend and his absence means that one of Vincent Aboubakar or Fabrice Olinga is likely to be called upon in Manaus.