Toulon lock Bakkies Botha is set for two months out after fracturing an eye socket against Sale in the Heineken Cup on Sunday.
The former Springbok international came off just before half-time and will have an operation later in the week.
The 33-year old has been an influential figure for Toulon so far this season, frequently starting alongside one of Jocelino Suta, Simon Shaw or Nick Kennedy, who will now all fill in for Botha in his absence.
Botha's injury will rule him out of the Round 5 and Round 6 Heineken Cup games as Toulon look to secure a top seeding for the quarter-finals, although they currently lead Pool 6 by five points ahead of Montpellier.
Toulon will also be without Botha for Top 14 clashes against Perpignan and Racing Métro amongst others.