Stormers hooker Tiaan Liebenberg has flown back to Cape Town from Australia on Monday due to a pinched nerve in his neck.
Liebenberg sustained the injury during the Stormers' loss to the Brumbies last weekend, their third straight defeat on tour.
Flanker Schalk Burger, who is beginning to return to form after a lengthy spell on the sidelines, damaged his calf hours before kick-off and has also flown home.
Fellow back-row Siya Kolisi is also out with a shoulder knock, while second-row Ruan Botha suffered an ankle injury.
Stormers boss Allister Coetzee reckons he will be without the hooker for around three weeks, but admits the picture is less clear regarding the other three forwards.
"Ruan injured the ankle that was operated on last year and, at this stage, he has a 50 percent chance of being fit for the next match against the Reds," Coetzee told SuperSport.
"We also expect Siya to be ready since he has responded well to treatment. In the case of Schalla (Burger) we'll wait and see what the specialist's report says before we know how long he'll be sidelined."
Hooker Scarra Ntubeni was also ruled out earlier in the tour, and with Liebenberg unavailable, flanker Deon Fourie must revert to his back-up position in the front row.
"Deon will start as a hooker this week and Stephan Coetzee, who joined us on tour last week, will be the reserve," added Coetzee.
"We have flown over Tazz Fuzani (lock) and Sikhumbuzo Notshe (flanker) as injury replacements and both of them will come in the reckoning for the match-day squad."