"I think Australia and India have proven it time and time again," said du Plessis after producing South Africa's first and only century of this World Cup.
"They are teams that win big games. It's hard to look past Australia and the success they've had in winning World Cups, as much as we would like to say we want to compete with that.
"The confidence that an Australian team comes into a World Cup with is just like an extra player on your team."
Du Plessis, asked to name t he winner of this World Cup, replied: "They (Australia) would probably prefer playing against New Zealand, but I would say one of Australia or India."