Is is difficult to justify replacement  of some of the players like Faf an Van der Dussen in the Protea team and there is only some indicators as tp their performance n first class crocket and compare that with what  camdidates achoeve on that level.  

Lets take the comparison between what Van der Dussen achievement as first change batsmen - a position where Du Plesis used to abt,   So lets look at first class cricket on that level:-

                                                 Van der Dussen           Du Plessis                 Van Toder  

Average   runs                                43.74                         39,53                          49,86

Strike rate                                      47,82                         46,82                          52,89

The difference is too big not to consider their replacement,

                                                     Elgar                      Roelofsen                     Rickelton

Average runs                                  42,01                        40,49                         42,55

Strike rate                                     45,94                         52,40                         53,77

Elgar's average and strike rate has been static for the last year, while - although being not much different in the average column - but Roelofsen  and Rickelton have  much higher strike rates than Elgar,