After being sent in to bat under heavy skies, South Africa laboured to 29 for two from 7.3 overs before persistent rain throughout the day ensured there would be no more play.
Buttler, who scored 103 in England's defeat by Pakistan in their second game, is the second highest run-scorer in the tournament with 185 at an average of 61.66.
That said, by the latter stages of a five-hour rain delay, du Plessis - who had yet to get off the mark in the first seven deliveries of his innings - admitted that his team's desire to get back onto the field had been tempered by the fear that a rain-shortened contest would have played into the hands of their opponents.
Had Rabada had the opportunity, du Plessis thinks this his strike bowler and new-comer Beuran Hendricks could have helped defend a small total. That is a strong sign of us as a team, as a culture, and that is one aspect of performance. He had bowled just four overs before walking off the field.
Next, Virat Kohli-led India handed them a six-wicket loss, meaning the elbow room for Du Plessis' team is increasingly getting narrow. The Proteas now needs to play fearless and attacking cricket. "We kind of made some mistakes at key points in the game and it happens in cricket, but you learn from it".
"We have to do the basics better, the batters have to take more responsibility".
Either way, South Africa would all too readily swap positions in the group table with West Indies. "A lot of other things had gone on before that, of course", he said.
"It is too far away", du Plessis said.
The abandoned match gifted the Proteas their first point of the tournament, following an unprecedented three straight losses. Both teams wanted to play and get results but you can't control the weather. We need to focus on our own performance and get that sorted out.