Stormers wing Kobus van Wyk has been ruled out of action for six weeks, after picking up a patella injury against the Western Force last weekend.
Van Wyk limped off the field in the 29th minute of Saturday's hard-fought Super Rugby clash in Perth – won 13-6 by the Stormers – and will be unavailable until June.
Stormers head coach Allistair Coetzee admitted that Wyk's injury was a big setback with a clash against the Bulls coming up.
"It's obviously a blow to lose a player like Kobus ahead of a big game like this, but we have players like Johnny Kotze, Huw Jones and also Pat Howard who are hungry for a starting opportunity," he said.
"We have a few days to mull over our selection options and will make those final decisions ahead of Thursday's team announcement."
Meanwhile, fellow wing Dillyn Leyds sat out training on Tuesday, but squad captain Duane Vermeulen – fresh off his two-week rest period – rejoined squad training.
The Stormers will host the Bulls at Newlands on Saturday.