The management will not want to burden Duminy with too much because his main focus should be batting. South Africa have looked uncharacteristically weak in that department, with only one half century coming from them, off the bat of Jacques Kallis. Their combinations at the top have not worked with Kallis unable to form a strong opening partnership with either Loots Bosman or Graeme Smith.
It may be an idea to move Herschelle Gibbs into the opening berth, so he can play his natural attacking game, while the captain's worrying form should see him drop to three. Albie Morkel was rightly used higher in the order and that trend should continue.
On paper, there is nothing wrong with the lineup, it's probably one of the strongest in the competition and it's not as though South Africa have better players sitting around than the batsmen they have in the team now. They're simply struggling with non-performance, and because all of them are going through a slight slump simultaneously, it shows.