India, who are top-ranked in Test cricket, are on 120 points in the ODI rankings, only one point behind South Africa and will go ahead if they win the first match in Dharamsala on Sunday.
India will reach 121 points and edge South Africa on decimal points if they take a 1-0 lead in the series but will have to also win the following two matches in Mohali and Visakakhapatnam on 13 and 17 December.
India will slip to 119 points even with a 2-1 win in the ODI series, which follows a three-Test series between the two sides, which India won 1-0.
On the other hand, eighth-ranked Sri Lanka will remain on 83 points even with a 3-0 loss but can go up to 87 points with a 3-0 series win.