Brazil defender Marcelo asked to be substituted in Brazil's 2-0 win over Serbia because of back spasm, Brazil head coach Tite said on Wednesday night.
The five-time World Cup champions beat Serbia 2-0 in their last group-stage match at Moscow's Spartak Stadium and advanced to the last 16 on Wednesday. Marcelo was substituted in the 10th minute.
"Marcelo left the pitch after several minutes, he suffered an injury" Tite said.
"The only thing I know is that he had a problem with his back. When I hugged him after the first half, he said that he had a backache. He said that it was a back spasm. Whatever it was, it was impossible to play with an injury."
Brazil will face Group F runners-up Mexico in the round of 16 match at the Samara Arena on Monday.
The 2018 FIFA World Cup kicked off on June 14 and will continue until July 15, with the matches being played in 11 cities across Russia.