Neymar sat crying on the bench and later left the stadium limping with a swollen right ankle after Brazil's 2-0 victory over Serbia.
Brazil team doctor Rodrigo Lasmar said Neymar sprained his ankle.
"We put ice on it while he was on the bench and then in physiotherapy," Lasmar said. "There is no test scheduled for now but we will schedule it if needed. He will be under observation. We will know more tomorrow."
Brazil coach Tite said he was "confident that Neymar will continue playing at the World Cup," but Lasmar said it was too early to comment on the extent of the injury.
Neymar was also injured at the 2014 World Cup. Playing at home in Brazil, his tournament ended with a back injury in the quarter-finals against Colombia when he had to be taken off the field on a stretcher. Brazil ended up losing to Germany 7-1 in the semifinals.
Neymar, who was fouled nine times in the match against Serbia, got injured in the second half and was substituted in the 79th minute. Tite said he stayed on the field for 11 minutes before asking to be replaced.
"He overcame the injury because the team needed him," Tite said. "I didn't even see that he had been injured. He just kept playing."
Brazil World Cup 2022 squad
Goalkeepers: Alisson, Ederson, Weverton
Defenders: Alex Sandro, Alex Telles, Dani Alves, Danilo, Bremer, Éder Militao, Marquinhos, Thiago Silva
Midfielders: Bruno Guimaraes, Casemiro, Everton Ribeiro, Fabinho, Fred, Lucas Paquetá
Forwards: Antony, Gabriel Jesus, Gabriel Martinelli, Neymar Jr., Pedro, Raphinha, Richarlison, Rodrygo, Vinicius Jr.
Head coach Tite has outlined an attacking approach for his side for the tournament, too.
“There will be opportunities for all [Brazil’s forwards],” Tite said in an interview with The Associated Press. “Whoever is in will be deciding the match, all have to be prepared. Every match might require a different characteristic.”
Who are the star names in the squad?
Paris St-Germain pair Neymar and Marquinhos will both be key for Brazil, not forgetting Real Madrid star Vinicius Jr.
What are Brazil’s fixtures?
What form are Brazil in?
Brazil will go to the 2022 World Cup in Qatar as the favourites and the top-ranked team as the latest Fifa rankings were released on October 6.
Twenty years since their last World Cup glory, the team will be looking to pick up the trophy for a sixth time at World Cup 2022 in Qatar. Back top of the Fifa world rankings once more, the Canarinha have lost just one game since the turn of 2021; by one goal to Argentina in the Copa America final.
Four teams qualified from CONMEBOL and Brazil finished top of the pile with 14 wins and three draws. Neymar finished as their top scorer with eight goals.
What is Brazil’s World Cup record?
Brazil are the most successful team in the tournament’s history. They’ve won the World Cup a record five times (1958, 1962, 1970, 1994, 2002) and have played in all 21 editions of the tournament so far.
In Russia 2018, Brazil were tournament favourites but crashed out at the quarter-final stage following a 2-1 defeat to Belgium.
Argentina | Australia | Belgium | Brazil | Cameroon | Canada | Costa Rica | Croatia | Denmark | Ecuador | England | France | Germany | Ghana | Iran | Japan | Mexico | Morocco | Netherlands | Poland | Portugal | Qatar | Saudi Arabia | Senegal | Serbia | South Korea | Spain | Switzerland | Tunisia | Uruguay | USA | Wales
Brazil are currently a best price of 10/3 and favourites to win the World Cup.