Brazil must do without injured star forward Neymar against Switzerland at the World Cup on Monday (at 11pm Cambodian time), while Cristiano Ronaldo looks to lead Portugal into the last 16 in Qatar.

Five-time world champions Brazil could secure a spot in the knockout phase with a win over the Swiss depending on the outcome of the day's early game between Serbia and Cameroon (at 5pm).

Brazil kicked off their campaign in Qatar with a 2-0 victory over Serbia in Group G, but Neymar limped off with a sprained ankle.

"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," said Brazil centre-back Marquinhos.

"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."

Ronaldo became the first man to score in five World Cups after converting a disputed penalty in Portugal's opening 3-2 victory over Ghana in Group H.

The Portuguese will qualify for the second round at the Lusail Stadium, which will host the final on December 18, if they beat Uruguay (at 2am).

Danilo Pereira has been ruled out of the rest of the group stage after fracturing three ribs in training, meaning 39-year-old Pepe is likely to start in defence.

It would make him the second oldest outfield player ever to appear in a World Cup match, after Cameroon great Roger Milla.

Cameroon lost to Switzerland in their first game so will attempt to bounce back against Serbia, who are being investigated by FIFA after the team hung a controversial flag depicting Kosovo in their changing room before their loss to Brazil.

South Korea coach Paulo Bento says the team will see a "different" Son Heung-min against Ghana (at 8pm) after the forward got used to his protective face mask during their 0-0 draw with Uruguay.

Before coming to Qatar, Son had surgery to repair a fracture around his left eye he suffered while playing for Tottenham Hotspur earlier this month.

"First he needed to feel at ease with his teammates and afterwards with the opponents. The second game will be different," said Bento.