Striker Majeed Waris is undergoing treatment at French Ligue 1 side Nantes after picking up a muscle injury.
The Ghana international missed the last Sunday's league match against Guingamp.
Waris failed to recover for Wednesday's Coupe de France quarter-final against lower division side Vitre.
The 27-year-old has scored four goals in 24 league appearances for Vahid Halilhodzic's side.