Adriaan Strauss is in a race against time to be fit for the start of Super Rugby next year after undergoing back surgery on Thursday.
The former Springbok captain picked up the injury on South Africa's November tour.
Bulls team doctor Herman Rossouw said there was a disc in Strauss' lower back which pinched a nerve. The hooker is the favourite to lead the Bulls in Super Rugby.
Meanwhile Lions winger Ruan Combrinck will be out for up to four months after having surgery on his injured shoulder. He won't be back before at least the sixth round of Super Rugby.