Neymar walked out of Brazil training on Tuesday in serious discomfort due to pain in his right ankle.
The Brazil striker was seen wincing and covered his face with a hand in distress, sparking fresh fears about his fitness.
He will spend the rest of the day undergoing physiotherapy, the Brazilian Football Confederation said.
‘He was feeling pain thanks to the large number of fouls he suffered in the Switzerland game,’ a spokesman told reporters.
‘He complained of pain and so he went to physio and he will train normally on Wednesday.
Neymar recovered sufficiently from a broken foot to play in his side’s World Cup opener against Switzerland but is continuing rehabilitation on the injury.
But he was accompanied off the training pitch at Yug Sport Stadium in Sochi where he had been working with his Selecao team-mates.
Two members of the Brazil staff trudged off with the 26-year-old when he was unable to continue.
On Monday, Neymar had posted a picture of his foot receiving treatment alongside the message: ‘Working hard.’
He broke his foot back in February while playing for the PSG, but updates on social show media that he is still receiving treatment to get it back up to 100 per cent.