Clermont and France hooker Benjamin Kayser's wretched run with injuries have continued, after he was ruled out for several months.
Kayser has suffered a cervical hernia and will now be sidelined for a matter of months, although a specific timeframe for his return is yet to be decided.
It leaves France in a tight spot at hooker, with Dimitri Szarzewski also ruled out through injury for the tour.
That leaves Guihelm Guirado and Christophe Tolofua as options for the number two jersey, with Philippe Saint-André expected to announce a third hooker for the tour in the next few days.
Clermont crashed out of the Top 14 playoffs last weekend against Castres, losing their unbeaten record at the Stade Marcel Michelin.