Brazil top Group G and next face Switzerland and Cameroon, without their talisman Neymar and ever-reliable fullback Danilo, though the team's doctor confirmed only that they would miss the Swiss game.
"Neymar and Danilo went through an MRI on Friday afternoon and we found ligament damage in the ankle of both of them," Rodrigo Lasmar told reporters.
"They will miss the next game for sure and we will be cautious as they will undergo treatment in order to try to get them in shape so they can play again in the World Cup."
Neymar has had problems with his right foot and ankle for several years and looked distraught when he left the pitch late in Thursday's match.
In the 2014 World Cup he suffered a back injury in the quarter-final victory over Colombia, ruling him out of the 7-1 semi-final defeat by Germany.
At Russia 2018, injuries again hampered his dream of winning the World Cup. Early in 2018, Neymar suffered a sprained right ankle that affected the fifth metatarsal in his foot.
He missed 16 games for Paris St Germain at the end of the 2018-19 domestic season and was never fully fit as he played through pain for Brazil in Russia until they were knocked out by Belgium in the quarter-finals.
The forward suffered similar injuries in 2019 and last year.
His replacement should be Real Madrid prodigy Rodrygo, who played in Neymar's position in Brazil's three practice games that Reuters had access to in Turin in the week prior to the World Cup.
However, the biggest question mark is regarding Danilo's replacement, as 39-year-old veteran Dani Alves is the only right back available.
The former Barcelona man played his last game for Mexican side UNAM Pumas in September and sustained a knee injury that has been troubling him since.
Brazil coach Tite tested Real Madrid centre back Eder Militao as a full back in their friendly match against Ghana and could be another option along with Liverpool midfielder Fabinho, who also has played as a right back before.
Adding to Brazil's problems, winger Antony and midfielder Lucas Paqueta are both ill and could also miss the match against Switzerland on Monday.
