Cape Town - The Proteas have dropped a place in the latest ICC ODI Team Rankings despite defeating Sri Lanka 3-2 in their five-match ODI series.
Ottis Gibson's side started the series in third position with 113 points, one more than New Zealand's 112 points.
South Africa had sealed the series with three successive wins, but Sri Lanka bounced back for two consolation victories to close the series.
The result saw the Proteas slip to 110 points to sit behind New Zealand in fourth position.
Meanwhile, Sri Lanka gained three points and moved to 80 points, although they remained in their pre-series eighth position.
England are currently on top of the table with 127 points while India are in second position with 121 points.
The Proteas' next ODI series will be against Zimbabwe in a three-match series starting on September 30 in Kimberly.