Van Wyk limped off the field in the 29th minute of Saturday’s hard-fought 13-6 victory in Perth and will be unavailable until June.
Fellow wing Dillyn Leyds sat out training on Tuesday, but squad captain Duane Vermeulen – fresh off his two-week rest period – rejoined squad training at the Stormers’ High Performance Centre in Bellville.
The Stormers, in second place in the closely-fought South African Conference, will host the Bulls at Newlands on Saturday.
“It’s obviously a blow to lose a player like Kobus ahead of a big game like this,” said Stormers coach Allister Coetzee. “But we have players like Johnny Kotze, Huw Jones and also Pat Howard who are hungry for a starting opportunity.”