The Stuart Broad show in Johannesburg not only destroyed South Africa but also dethroned the Proteas from the No.1 Test rankings.
Now India, with 110 rating points, are the No. 1 team in ICC Test rankings, with Australia one rating point shy in second place.
India had defeated South Africa 0-3 at home in December, which saw the lead enjoyed by the Proteas cut to just four points.
Thus South Africa had to either draw or win the four-Test home series to retain the No. 1 position.
Even if the hosts win the last Test, a 2-1 series defeat will mean they will slip to 109 points, behind India and Australia, who are both on 110 points.
However, India are ahead of Australia on decimal points. Their position will reflect in the fresh rankings, which will be released at the end of the series in South Africa.
If they lose the final Test too, the Proteas will slip to fourth in the rankings table. The last time India were No. 1 in Test rankings was in August 2011; they were dethroned by England.