France backrow forward Anthony Jelonch is recovering from a calf injury which has ruled him out of the start of the Six Nations, club side Toulouse confirmed on Tuesday.
Toulouse said that tests revealed a slight muscle injury, with the player expected to be sidelined for a few weeks.
The 28-year-old played the full 80 minutes at No 8 in Toulouse's 80-12 Champions Cup thrashing of Leicester on Sunday.
Jelonch's withdrawal comes as a cruel blow to a player who only returned to competition in September after an eight-month lay-off for an anterior cruciate ligament injury in his right knee.
He will be replaced in the 42-man France squad by Racing 92 lock Romain Taofifenua who was initially ruled out of contention.
France begin their campaign against Wales in Paris on 31 January 31.