Pretoria - The Bulls will have to face the Sharks in Saturday's season opener of the Super Rugby competition without Arno Botha, Morne Mellett and Jesse Kriel, the union said on Monday.
According to Bulls team doctor Org Strauss, flank forward Botha would undergo surgery on his injured ACL (anterior cruciate ligament) this week and he would be out of rugby for at least six months.
Mellett was still two weeks away from returning to action as he was recovering from a back injury while Kriel's contused calf will take another three weeks to heal.
The rest of the squad had been declared fit, although Deon Stegmann would only start training on Wednesday as he was recovering from a groin strain.
Bulls coach Frans Ludeke was expected to name his team for Saturday's clash on Wednesday.