The Stormers have lost newly capped Springboks flanker Siya Kolisi for the rest of the Super Rugby season with a torn ankle ligament.
The Stormers said on their Twitter feed on Monday that Kolisi would be out for six weeks, also putting him in doubt for the start of the Rugby Championship.
Kolisi was due to return the week South Africa opens its Rugby Championship campaign at home to Argentina on August 17. The Stormers said Kolisi did not require surgery.
The 22-year-old loose forward made his Springboks debut against Scotland last month, winning the Man of the Match award after coming on as an injury replacement in the opening minutes.
The Stormers have two regular-season games left in Super Rugby and only an outside chance of making the play-offs.