St Etienne captain Loic Perrin faces up to six months on the sidelines after rupturing his anterior cruciate ligament.
The 26-year-old suffered the injury during a French League Cup match against Bordeaux on Wednesday.
The midfielder will undergo surgery this week and has been ruled out for between five and six months.
Speaking to L'Equipe St Etienne manager Christophe Galtier said: "Its bad news for Loic, he is very upset.
"I am sure he will face the situation head-on and will return stronger and in top form after the winter break."