Montpellier - Springbok prop Jannie du Plessis faces six weeks on the sidelines while All Black flyhalf Aaron Cruden will also miss Saturday's trip to Stade Francais, Top 14 leaders Montpellier said on Tuesday.
Springbok international Du Plessis, 34, is suffering from a knee ligament strain and has yet to play a match this season.
He was initially suspended and then recovering from an elbow problem.
His last match was the Top 14 playoff defeat to Racing 92 in May.
Cruden injured his ribs in Sunday's 54-10 thrashing of Brive and will miss the trip to Paris.
The 28-year-old should be replaced in the No 10 jersey by South African Francois Steyn.
Montpellier will also be without Australian back Joe Tomane, who has a knee injury, and Fijian wing Timoci Nagusa, who has spent three days in hospital with pneumonia and won't be back in training until next week.