Brazil star Neymar hobbled out of training with Brazil ahead of its Group E clash with Costa Rica on Friday.
Neymar was absent from training on Monday, missing the session a day after Brazil drew 1-1 with Switzerland in its opening World Cup clash.
The Paris Saint-Germain forward received some tough treatment from Switzerland, being fouled 10 times during the game, his first competitive start since February.
Follow: FIFA World Cup 2018
A fractured foot kept Neymar out of the end of PSG's season but he made a goalscoring return to action with a stunning solo strike against Croatia in a friendly at Anfield, and was also on target in a 3-0 warm-up victory against Austria.
Tite's men looked set to receive a boost with Neymar taking part in Tuesday's session.
But after around 10 minutes he limped away with a member of staff to receive some treatment after looking clearly uncomfortable on the field.
However, later in the day, sources say it looks like an ankle problem for the forward and the Brazil talisman should, in all probability, be able to train on Wednesday.
