France captain Patrick Vieira has given himself until the end of the week to prove his fitness for Euro 2008, reported BBC.
The 31-year-old Inter Milan star hurt his left thigh last Friday and will miss the opening Group C game against Romania in Zurich on Monday.
"If by the end of the week I am not training with the squad that would mean I will not be participating in the Euros," said the former Arsenal star.
Fellow midfielder Mathieu Flamini, 24, has been called up as cover.
Flamini, who has agreed a deal to join AC Milan from Arsenal on July 1, was in an initial 30-man squad but did not make the final cut of 23.
Team spokesman Yann Le Guillard said no French player had pulled out of the squad to make way for Flamini and he will fly with the squad to Switzerland on Wednesday.
Vieira revealed he has a "little tear" in his thigh but believes he still has a good chance of making the final two group games.
"It is nothing serious but unfortunately it has happened at a bad time - because every day counts now and the tournament is approaching," he added.
"Now, what I have to do is try to recover as quickly as possible. I am still optimistic."
France are in the same group as world champions Italy, the Netherlands and Romania.