Skipper Jonathan Mills, who recently signed for Llanelli Scarlets, is replaced at lock by Alun Wyn Jones of Swansea and Richard Dale, the Newport flanker gives way to Tom Brown of Hartbury College in the pack, while the centres Gavin Evans and Steven Ireland are replaced by Andrew Bishop and Lee Thomas.
Flanker Jonathan Edwards of Pontypridd, who was a late call-up when Richie Pugh joined the senior side in Argentina, has been awarded the captaincy for this vital match.
South Africa won their opening match by 69-15 against hosts Scotland, while Wales defeated Russia by 46-11.
The Wales side is: - 15 Ricky Williams; 14 Matthew Nuthall, 13 Andrew Bishop, 12 Lee Thomas, 11 Chris Czekaj; 10 Nick Macleod, 9 Richie Rees; 1 John Yapp, 2 Kieran Crawford, 3 Cai Griffiths, 4 Alun Wyn Jones, 5 Ian Evans, 6 Tom Brown, 7 Jonathan Edwards (capt), 8 Gavin Quinnell.
Replacements: 16 Ian George, 17 Will Kay, 18 Jonathan Mills, 19 Richard Dale, 20 James Ireland, 21 Matthew Jones, 22 Steven Ireland.