Bordeaux flanker Cameron Woki was drafted into the France squad for the opening Six Nations game against Italy following the withdrawal of Gregory Alldritt, the French federation announced on Thursday.
The FFR gave no explanation for Alldritt's withdrawal from the 37-man squad and he remains in line to play for La Rochelle against Bayonne in the Top 14 on Friday.
La Rochelle put out a statement on their website Thursday saying that Alldritt, a regular in coach Fabien Galthie's first-choice backrow alongside Francois Cros and captain Charles Ollivon, would "undergo medical examinations at the very beginning of next week".
The statement said the examinations might put him out of action for "a few days" and prevent him from joining the French squad next week.
"The decision was therefore taken, in consultation with the player and the staff of the XV of France, to hold on to him during the first week of preparation for the Blues."
Woki, who has four caps, made his international debut as a replacement in last year's Six Nations win over England in Paris and he also featured in the victory over Italy.
His first start came against Italy in the Autumn Nations Cup and, with most of the first choice players not available for the final, the 22-year-old also impressed against England at Twickenham.
He hobbled off the field 10 days ago during Bordeaux's 31-9 win over Lyon, suffering from a "small sprain of the right ankle", according to his coach Christophe Urios.
The French gather in Nice on January 25 to begin their preparations before kicking off in Italy on February 6, if the coronavirus situation allows the competition to go ahead.