sharks backline

 15 Odwa Ndungane, 14 JP Pietersen, 13 Louis Ludik, 12 Meyer Bosman , 11 Lwazi Mvovo, 10 Riaan Viljoen, 9 Charl McLeod, 8 Keegan Daniel (c), 7 Jean Deysel, 6 Marcell Coetzee, 5 Franco van der Merwe, 4 Edwin Hewitt, 3 Jannie du Plessis, 2 Bismarck du Plessis , 1 Tendai Mtawarira

Could someone help me understand, why the sharks aren't playing the following backline:

15 ludik, 14 odwa (where he can do the least damage with his soft running and tackling), 13 JP (where he's played some OK matches in recent history)

 not sure, but Riaan Viljoen at 10 must be the worst mistake. 

They probably a bit thin at centre. I'd rather use JP at fullback and Odwa on the wing!