Pavel Nedved sustained a possible knee injury during training with the Czech Republic on Thursday after colliding with team-mate David Rozehnal.
The Czech Republic hope Nedved's injury is not serious
Doctors dealt with the midfielder's knee for 15 minutes and the Juventus star spent the rest of the session slowly running on the side of the field
"The knee hurts and that forced him to quit training," said Czech team physician Dr Petr Krejci.
"We hope that it won't be anything serious and he will be fit."
Nedved came out of international retirement to help the Czechs qualify for the World Cup.
He is expected to be one of the team's leaders - along with Arsenal midfielder Tomas Rosicky, who recovered from a thigh injury earlier this week.
Nedved, the 2003 European player of the year, has scored 18 goals in 87 appearances for the national team.