The Proteas have slumped to the seventh in the ICC Men’s Test Rankings on Thursday – their joint-lowest position ever.
The governing body provided an updated rankings list, on which the South Africans were overtaken by the West Indies, whom they are set to play in June.
The Proteas beat Sri Lanka 2-0 in a Test series on home soil over the festive period, but suffered a disappointing 2-0 defeat by Pakistan in the subcontinent at the beginning of this year.
England, though, have overtaken Australia in the Test rankings to move to third, while New Zealand occupy second place and India sit atop the rankings.
The Black Caps and Virat Kohli’s charges will square off in the World Test Championship final in Southampton next month.