France scrum-half Morgan Parra requires knee surgery which will rule him out of the rest of the Six Nations.
Parra's club, Clermont Auvergne, say the 29-year-old will be sidelined for up to six weeks and faces a race against time to be fit for their Champions Cup quarter-final against Toulon on April 1.
"Having observed three weeks of complete rest, Parra will have to undergo arthroscopic repair of his knee," read a club statement.
"The surgical procedure will require a period of unavailability of between four to six weeks."
France have lost their first two Six Nations games - 15-13 against Ireland and 32-26 to Scotland in Murrayfield last Sunday.
They take on Italy in Marseille on February 23, face England at the Stade de France on March 10 and end their campaign in Wales the following week.
Defending Top 14 champions Clermont sit 10th after losing nine of their 16 fixtures. They travel to Lyon on Saturday, live on Sky Sports Action from 7.40pm.