Brazil have confirmed Fred may require a scan on an ankle injury sustained in training.
The midfielder is set to join Manchester United after the Premier League club agreed a deal with Shakhtar Donetsk.
But Fred's place at the World Cup could be in doubt after he went down hurt during Thursday's session.
Brazil team doctor Rodrigo Lasmar said Fred will be monitored, with Tite's men set to play Austria on Sunday in their final friendly before Russia 2018.
"Today Fred had trauma in his ankle but it is too early to say anything about it," Lasmar said.
"Tomorrow we watch to see what happens and then decide if we need to do any exams or not.
"But at the moment it is too early to say anything about him."