Cape Town - It is a decision that is unlikely to be popular given how immense he has been in the Springbok No 7 shirt this year, but Pieter-Steph du Toit could be set for a move back to the second row for Saturday's Test against England at Twickenham. 

Coach Rassie Erasmus opened that door on Monday when discussing who would start in the No 5 shirt now that Franco Mostert has been ruled out. 

Eben Etzebeth is almost certain to keep going at No 4, but Erasmus must now ponder who his lock partner will be. 

Lood de Jager is fit again and with the Boks in England, but he has not played any rugby in months and would surely be more suited to a bench role. 

RG Snyman, meanwhile, is considered more of a No 4 option by Erasmus, but could certainly fill a gap as the lineout general for a Test. 

Then there is JD Schickerling, who was perhaps the most surprising pick in the squad for the tour. 

Schickerling's inclusion would have had everything to do with the uncertainty surrounding the availability of Mostert, and his management at the lineout has been a standout feature throughout the Currie Cup this year. 

There are options, and lock is a position where the Boks have had abundant depth for some time now. 

Du Toit has been one of the Boks' biggest players this year, with most of those hair-raising performances having come from the side of the scrum. 

His heroic defence, limitless engine, ball-carrying power and the fact that he remains a serious lineout option have all contributed to him ticking all the boxes as a Bok No 7. 

But, listening to Erasmus speak on Monday, it sounds like the 26-year-old could be set for yet another shake-up in a Bok career that has seen him race to 42 caps. 

In discussing how Mostert would be missed against England, Erasmus went straight to Du Toit in listing possible replacements. 

The good news is that there is no doubt that Du Toit is flexible enough to make the change once again. 

He has started 10 Tests at lock and 12 at flank, but Du Toit is a monster and his work rate is not dependent on the number on his back. 

Where things do get interesting, though, is what a Du Toit shift back to lock would mean for the loose trio. 

There are no other traditional No 7, specialist ball-carrying options in the Bok squad, meaning that that Erasmus might have to get creative. 

Francois Louw started the last Rugby Championship Test against the All Blacks at No 8, but he is unavailable for the England game. 

Erasmus does have Warren Whiteley fit again and Duane Vermeulen available once more, while Sikhumbuzo Notshe is another loose forward option. 

Captain Siya Kolisi, meanwhile, has played at No 7 under Erasmus. 

Kick-off on Saturday is at 17:00 (SA time).