The Bulls have lost seven players to injury on their Australasian tour and Peter Grant will miss the Stormers tour.
Locks Flip van der Merwe and Grant Hattingh are the latest duo to be ruled out of the tour. Winger Bjorn Basson could become the eighth player to leave the tour early if he fails a fitness test later in the week.
The Bulls, who beat the Blues and then lost to the Crusaders and Reds, play the Brumbies in their final tour outing.
Stormers flyhalf Peter Grant will be out for longer than four weeks because of an ankle injury.
It was confirmed that Grant would not travel overseas with the team.