Juan de Jongh left the field early in his team's clash with the Cheetahs with concussion, which will rule him out of the match with the Sunwolves at Newlands on Saturday, while Shaun Treeby will be sidelined for two weeks with a rib injury.
The Stormers already lost centre Daniel du Plessis after the 22-year-old dislocated his shoulder last week while playing for Western Province.
The good news for the Stormers is that Springbok centre Damian de Allende returns to full training with the Stormers this week after recovering from a quad injury. This should be good news for Robbie Fleck, with the Stormers back on form.
De Allende could partner EW Viljoen in the midfield for the clash against the Sunwolves.
In other injury news, fullback Sarel Marais injured his knee after landing awkwardly and sustained no major ligament damage, but his progress will be monitored weekly as to how he responds to treatment.
Props Oliver Kebble (thigh) and Alistair Vermaak (calf) are still recovering from their respective injuries. Both players face a race against time to be fit for the Super Rugby quarterfinals.
The Stormers already secured their position in the tournament play-offs after topping Africa Conference 1.