Two-time major winner Carlos Alcaraz retired hurt from the Rio Open on Tuesday after two games due to a right ankle injury.

The retirement at 1-1 meant Brazil's Thiago Monteiro advanced, to meet compatriot Felipe Meligeni Alves for a place in the quarter finals.

Alcaraz, who twisted his ankle in the first game after only two points, received medical attention, broke Monteiro's serve, but after the Brazilian pulled level he shook his rival's hand and left the court walking as his coach Juan Carlos Ferrero looked concerned.

The Spaniard said his doctors said the injury was not serious.

“These things happen, even more so on clay,” the world No. 2, who was runner-up last year and winner in 2022 here, said. “It was not a problem of the court, I got injured as I switched direction. That happens in this kind of surface.”

The 20-year-old Alcaraz said he does feel pain when he walks and that he will have medical scans on Wednesday.

Monteiro said it was strange to go through after playing so little time against Alcaraz.

“On the court it didn't look so serious but then I saw it in the big screen and it was a bad twist. Now I can only cheer for him to recover, he is a star, a dominant one in the new generation," the Brazilian said.

Earlier, Stan Wawrinka was beaten 7-5, 6-4 in the first round by Argentina's Facundo Díaz Acosta.