Cardiff Blues expect Rhys Thomas and Andries Pretorius to miss October's Pro12 matches.
Hooker Thomas needs a knee operation to cure a cartilage problem, while flanker Pretorius is out for three weeks with a hamstring strain.
With Gareth Williams (neck) and Kristian Dacey (shoulder) already out, Thomas' absence leaves youngster Rhys Williams as the Blues' only fit hooker.
Martyn Williams (arm), Ben Blair (knee) and John Yapp (calf) are also injured.
But the injury crisis is set to ease before Saturday's league match against Glasgow Warriors with Ceri Sweeney, Gareth Davies, Chris Czekaj and Tom James available for selection.