Brazil are confident that Neymar will return to lead their bid to win a sixth World Cup despite the world's most expensive player suffering an ankle injury in their opening match in Qatar.

The Brazil captain came off late on in Thursday's 2-0 win over Serbia with what was later diagnosed as a sprained ankle and has since been ruled out of their second Group G outing against Switzerland on Monday.

Doubts have even been raised in some quarters that he might struggle to feature again at the tournament, which finishes with the final in Doha on December 18.

But defender Marquinhos, who is also a teammate of the forward at Paris Saint-Germain, said Neymar has since been spending his days undergoing intensive physiotherapy in an attempt to recover full fitness as soon possible.

"At the time it was difficult for him and after the game he was sad which I think is normal given how much he has dreamt of this," centre-back Marquinhos said at a press conference in the Qatari capital on Sunday.

"Now, after the tests and the treatment, he is doing physiotherapy 24 hours a day which shows how much he wants to be back with us.

"We don't know when, but we hope it's as soon as possible."

Brazil coach Tite insisted in the immediate aftermath of the win over Serbia that the 30-year-old Neymar would definitely play again at the tournament, but this time he was rather more measured when pressed on the subject of the superstar's fitness, as well as that of right-back Danilo.

"I believe that Neymar and Danilo are going to play again at this World Cup. I do. But medically, clinically, I am in no position to say anything," he admitted.

"I will keep doing so, not just for Neymar but also Danilo. I believe we are going to be able to use them again."

A Brazil win against Switzerland at Doha's Stadium 974 could be enough for them to secure a place in the last 16 with one group game to spare, depending on the result of the earlier Group G match between Cameroon and Serbia.

They would then play a last-16 tie on either December 5 or 6.