The Springboks will end the year as the number one side for the third year in succession, regardless of what happens at the Principality Stadium this weekend.
The Springboks can only lose a maximum of three points in defeat by Wales, which will leave them still 0.61 rating points above New Zealand in second.
South Africa cannot improve their rating with a victory over Wales due to the 19.71 points between the teams before home weighting is factored in.
Even a win by more than 15 points would not be enough for Wales to climb from 11th.