Afghanistan reached 69/2 and seemed well set - even if they then lost their third wicket, Hashmatullah Shahidi edging Andile Phehlukwayo to slip for eight, in the first over after the second rain delay. Guys like Quinton, they're on a different level when it comes to attacking and playing free all the time, ' said du Plessis.
Speaking after the match, an elated du Plessis said: "Today was a good day for us".
Rashid Khan swung his bat around towards the end of the innings, top-scoring with 35 off 25, and with the interruptions reducing the contest to 48 overs a side, the DLS method left South Africa needing 127 to win. De Kock brought up his half-century off 58 balls but was caught at mid-wicket for 68.
South Africa must focus on the "now" and as long as there is a chance of making the semi-finals, then that is where their heads must be.
After three straight losses against England, Bangladesh and India, their fourth match against the West Indies was abandoned due to rain.More news: Pelicans' Julius Randle declines player option, enters free agency
Defeat would have seen the sun go down on their bid to make the semi-finals.
Although South Africa played with greater intensity than in their previous matches, it was hard to gauge their improvement accurately given the kamikaze nature of Afghanistan's batting. Phehlukwayo chimed in with two wickets of his own, and he also performed a crucial holding role, stringing together 36 dot balls as Afghanistan's hit or miss (and today, it was usually miss) tactics backfired.
Du Plessis did not want to get too carried away with the victory just yet though, but was ready to take the confidence gained from Saturday into this week's all-important clash with an in-form New Zealand team in Birmingham.
Chris Morris contributed with figures of 3-13 and Phehlukwayo took two wickets.
Before the second break for rain, Afghanistan appeared on the brink of building a reasonable score.More news: Ocasio-Cortez says pressure to impeach Trump grows every day
Man of the match Imran Tahir: "I really enjoyed that".
Rain and Afghanistan clearly do not get on at this tournament.
Opener Hazratullah Zazai pulled a delivery from paceman Kagiso Rabada and was caught by Rassie van der Dussen running in from the boundary for 22 off 23 balls.
The Proteas knew that a swift victory would help boost their net run rate but Afghanistan bowled well with the new ball, forcing Amla and Quinton de Kock to be watchful before earning the right to expand their strokeplay.
South Africa kept an unchanged lineup from its washout against West Indies, with fast bowler Lungi Ngidi given more time to recover from a hamstring injury. The captain, however, insisted that there was no time to relax as now the South Africans would need to win all their remaining matches in order to make the semifinals of the World Cup.More news: Ajax name price for Arsenal target, Hakim Ziyech