Brazil were sweating on the fitness of Neymar on Friday after their talisman sprained his ankle in the World Cup win over Serbia.
The forward suffered the injury in a collision with Nikola Milenkovic during the second half of the 2-0 win in Qatar on Thursday in Brazil's opening match.
The 30-year-old Paris Saint-Germain player attempted to continue but was substituted with about 10 minutes to go, shortly after Richarlison put Brazil two goals ahead.
Neymar was seen limping heavily after the game in Doha and photos showed swelling on his right ankle.
He declined to speak to journalists as he left the stadium, but posted a light-hearted message on Twitter, without making reference to his injury.
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"Tough game but it was important to win," he said. "Congratulations team, first step taken... six to go."
Team doctor Rodrigo Lasmar said it was too early to jump to conclusions.
"We need to wait 24 to 48 hours to have a better assessment," said Lasmar. "We have not scheduled any MRI (scan) and tomorrow we'll have a new assessment.
"We need to wait, we cannot make any premature comments about his evolution."
Coach Tite was optimistic that Neymar would be back to lead Brazil's bid for a record-extending sixth World Cup crown.
They next face Switzerland on Monday, with their final Group G match against Cameroon.
"You can be certain that Neymar is going to play in the World Cup," Tite said, adding that the attacker had initially stayed on the pitch after hurting his ankle "because the team needed him".
Brazil struggled to impose themselves in the first half against Serbia before finding their spark.
Richarlison poked home from close range shortly after the hour mark and then produced an acrobatic finish to double the lead.
PELE RECORD
Neymar follows in a long tradition of great Brazilian number 10s and needs just two goals to equal Pele's all-time record tally of 77 for the South American nation.
Brazil boast an impressive array of attacking talent including Raphinha, Richarlison and Vinicius Junior and they were able to bring Rodrygo and Gabriel Jesus off the bench against Serbia.
But Neymar, who is playing in his third and possibly last World Cup, is the player who makes the team tick.
The Brazilian's career has though been peppered by injuries which have impacted on his previous two World Cups.
In 2014 he suffered a fractured bone in his back in the quarterfinal win over Colombia before the hosts were humiliated by Germany in the semifinals, losing 7-1.
Four years later he raced to recover from injury in time for the tournament in Russia, but Brazil never hit the expected heights before losing to Belgium in the last eight.
The former Barcelona star, who has 122 caps for Brazil, also missed the 2019 Copa America after suffering torn ligaments in his right ankle.
In 2021 Neymar was out for about 10 weeks of the French season after suffering ligament damage to his left ankle.
This time he arrived fit and firing in Qatar after a fantastic start to the season with PSG, in which he has scored 15 goals in 20 games.
His latest issue could prove just to be a scare. But until we know more, a nation will be holding its breath.