The Stormers will face the Brumbies at Newlands on Saturday without lock Ruan Botha while centre and vice-captain Juan de Jongh is also doubtful.
Botha suffered an ankle injury in Saturday's 25-17 defeat to the Cheetahs and De Jongh has a hip pointer injury which saw him come off in the 23rd minute.
The extent of Botha's injury was revealed via a Stormers press statement on the Cape Town-based franchise's official website.
"Lock Ruan Botha (torn ankle ligaments) could be out for three to six weeks," it read.
"He is in a moon boot at the moment, but at the Springbok training camp until Wednesday evening. The Stormers team doctor will see him on Thursday to make a final call on the length of his lay-off, but he is definitely out of action this week.
"Outside centre Juan de Jongh has a hip pointer injury. It’s normally a ten-day injury, but more will be known about his availability when he returns from the Bok training camp."