Sri Lanka - who shocked England so spectacularly in Leeds last week - must now beat West Indies and India in their final two games if they are to stand any chance of making the final four.
Former champions Sri Lanka are all but out of the tournament after the Islanders produced a dismal batting show to manage a modest 203, a target which the Proteas overhauled with 76 balls in hand.
Sri Lanka, who won the tournament in 1996 before making consecutive finals in 2007 and 2011, enter the 2019 edition on a difficult recent run of form.
New Zealand beat Sri Lanka by five wickets in the first T20I of the three-match series in Pallekele.
It all starts in Guwahati on Sunday as the biggest city in Assam is slowly getting back to normalcy after protests against the Citizenship Amendment Act (CAA).
Images from Friday's World Cup match between South Africa and Sri Lanka, at Chester-le-Street.
The convincing win gave India an unassailable 1-0 lead in the three-match series.
India would be desperate for the likes of Mahendra Singh Dhoni to find some form ahead of the semi-final when they take on Sri Lanka in their last preliminary World Cup clash, in Leeds, on Saturday.
590 cricketers -- including 370 Indian players and 220 overseas players -- will go under the hammer during the two-day mega auction in Bengaluru on February 12 and 13.
Three-time champions India continued their invincible run to enter the ICC Under-19 World Cup final for a fifth time after an emphatic 97-run victory over Sri Lanka in the first semi-final, in Mirpur, on Tuesday.
Rajneesh Gupta profiles the cricketers playing the World Cup 2019.
Rajneesh Gupta presents all the fascinating career numbers of players in the World Cup.