Morné Mellett has been ruled out of rugby for at least six months.
The 26-year-old prop is suffering from vertebral artery dissection and will not return to the field again this year.
Props Justin Forwood (rib), Neethling Fouche (ankle) and Dayan van der Westhuizen (shoulder) will return to the training field in two weeks, team doctor Org Strauss confirmed.
Fullback Jurgen Visser has been cleared to return to the training field next week. He is returning from a hamstring injury that ruled him out of Friday's match against the Canon Eagles in Japan.
Pierre Schoeman (knee) and Ruan Steenkamp (knee) will be back in three weeks.
Duncan Matthews and Ryan Nell should be able to play again at the end of August, following knee surgery. Irne Herbst and Piet van Zyl (knees) are out for the season, as is Dennis Visser (ankle).