Captain Thierry Dusautoir is set to miss France's autumn internationals after injuring his knee ligaments in Heineken Cup action for Toulouse.
Club coach Guy Noves confirmed the 54-cap flanker will be out for up to six weeks after twisting his knee in a tackle in their 33-21 win over Treviso.
"He suffered a twisted lateral ligament with a slight tear," said Noves.
France play the first of their November Tests in three weeks against Australia, followed by Argentina and Samoa.
"It's an injury that necessitates between four and six weeks rest according to his ability to properly recuperate," continued Noves.
"It's a hard hit for him and also Toulouse which will have to do without him while the club faces some tough challenges ahead."
France coach Philippe Saint-Andre said he wanted to see "how the injury evolved" before potentially replacing Dusautoir in his initial 33-man squad, adding that a decision would be taken during a meeting of backroom staff on Tuesday.
In the absence of Dusautoir, the captaincy is set to pass to experienced lock Pascal Pape, who skippered the team during the summer tour to Argentina when Dusautoir was left at home to rest.
Saint-Andre has included 18-year-old Toulouse centre Gael Fickou, who scored a superb solo try against Leicester last weekend, and 18-year-old Toulouse hooker Christopher Tolofua - who made his France debut on their summer tour of Argentina - in his squad for the autumn Tests.
Alongside Fickou, the other uncapped players are the Toulon trio of lock Jocelino Suta, flanker Pierrick Gunther and wing Vincent Martin, Stade Francais fly-half Jules Plisson, Racing Metro prop Eddy Ben Arous, Castres prop Yannick Forestier and Perpignan lock Sebastien Vahaamahina.
Forwards: Nicolas Mas (Perpignan), David Attoub (Stade Francais), Eddy Ben Arous (Racing Metro), Vincent Debaty (Clermont Auvergne), Thomas Domingo (Clermont Auvergne), Yannick Forestier (Castres), Dimitri Szarzewski (Racing Metro), Christopher Tolofua (Toulouse), Benjamin Kayser (Clermont Auvergne), Pascal Papé (Stade Francais), Yoann Maestri (Toulouse), Sébastien Vahaamahina (Perpignan), Jocelino Suta (Toulon), Thierry Dusautoir (Toulouse), Wenceslas Lauret (Biarritz), Fulgence Ouedraogo (Montpellier), Damien Chouly (Clermont Auvergne), Louis Picamoles (Toulouse), Pierrick Gunther (Toulon)
Backs: Morgan Parra (Clermont Auvergne), Maxime Machenaud (Racing Metro), Frédéric Michalak (Toulon), François Trinh-Duc (Montpellier), Jules Plisson (Stade Francais), Maxime Mermoz (Toulon), Wesley Fofana (Clermont Auvergne), Florian Fritz (Toulouse), Gaël Fickou (Toulouse), Vincent Clerc (Toulouse), Yoann Huget (Toulouse), Benjamin Fall (Racing Metro), Brice Dulin (Castres), Vincent Martin (Toulon).