South Africa won the opener on Wednesday by nine wickets and then made it two out of two by winning the second match at six runs to take the series 2-0.
Pakistan, which entered the series in second position and had an opportunity to top the rankings, has dropped behind Sri Lanka (128 ratings points), India and South Africa (both 123 ratings points) in fourth position on 120 ratings points - ahead of the West Indies by a fraction of a point, according to ranking released by ICC on Saturday.
The series result means South Africa has collected five ratings points and has joined India on 123 ratings points but will be ranked below Mahendra Singh Dhoni?s side by one-hundredth of a decimal point.
Pakistan and Protease will now lock horns in a two-match series to be played on November 20-22 in Johannesburg and Cape Town respectively.