The Manchester United midfielder spoke to reporters in Teresopolis as they continued preparations for the tournament.
The Santos FC star is currently sidelined with a grade two calf injury, but Casemiro remains convinced the all-time leading scorer can still play a decisive role on football’s biggest stage.
"Every time I come here, I have to talk about him,” said Casemiro.
"It was actually good that the doctor came here so there wouldn't be so many questions about him. Of course, no player likes to be injured, but I hope he is healthy enough to play; we need everyone.
“The evolution goes day by day and we are anxiously waiting for all players to be available. Everyone is important, including Neymar."
Despite Neymar facing up to three weeks out with injury, potentially missing Brazil’s opener against Morocco, Casemiro dismissed suggestions the forward can no longer lead the Selecao at the 2026 World Cup.
"That's you saying it, that he won't be the protagonist," he continued.
"A player, despite knowing what he does on the pitch, every one of them wants to have the protagonist role. That question is for Neymar, for the Mister... we know his quality.
“He is taking care of the injury, he wants to get back to training first. It has to be in stages. Get healthy again, get back to playing, and then think about being the protagonist. Think about health."