The Bulls on Monday were holding thumbs that the tactical ace would be available after all, but team doctor Org Strauss said on Tuesday morning that it was in the best interests of the player that he did not play in the South African derby.
Strauss added that the injury was more serious than first thought and Du Preez has immediately started with his rehabilitation. Heini Adams, who has had limited time on the field this season, is certain to replace Du Preez and Francois Hougaard will be on the bench.
The Bulls announce their team for Saturday's match on Wednesday.