Brazil forward Neymar hobbled out of training three days before their World Cup group game against Costa Rica on Friday.
The 26-year-old, who returned from a broken foot shortly before the tournament, withdrew from the session for treatment on his right ankle.
A Brazil spokesman linked the injury to Neymar being repeatedly fouled in Sunday’s 1-1 draw with Switzerland.
“As soon as he felt the pain he went to the physio,” said Vinicius Rodrigues.
“He will stay there for today and tomorrow morning, and will train as normal tomorrow.”
Paris St-Germain’s Neymar had surgery on a broken metatarsal in his right foot in February, causing him to miss the rest of the season.
He returned for Brazil’s penultimate World Cup warm-up game against Croatia in Liverpool on 3 June, capping his substitute performance with a stunning solo goal.
He scored again in their final friendly – a 3-0 win over Austria – before Tite’s squad left for Russia.
Neymar played 90 minutes of Brazil’s Group E draw with Switzerland, but did not take part in training on Monday at their base in Sochi.
Brazil face Costa Rica in St Petersburg 13:00 BST on Friday.
Neymar’s 2014 World Cup campaign was ended by a fractured back in the quarter-final win over Colombia.
Share your thoughts