Ghana winger Andre 'Dede' Ayew will be out for 10 days after injuring his left groin during international duty.
The absence of the 21-year-old, whose national team played Swaziland and Brazil last week, is a blow to his French club Marseille.
"The Marseille player injured his groin during Ghana's Nations Cup qualifier at home to Swaziland last Friday," Ghana's FA said on its website.
He will miss Saturday's Ligue 1 match at home to Rennes and next week's opening Champions League group match against Olympiakos in Athens.
The former European champions have been drawn in Group F, with Arsenal of England and Germany's Borussia Dortmund completing the pool.
After four games of the French league season, Marseille lie 16th in the 20-team league - without a win to their name.