Victory over the Proteas at Old Trafford would make sure that reigning champions would stay at the top of the points table.
Staying at the top would mean that Australia will face New Zealand in the semi-finals – a side they have already thumped in this tournament and in the 2015 World Cup finals.
"It's about maintaining the momentum of winning," Australia coach Langer said at Old Trafford on Thursday. "That's really important for us.
"For this game, some people said it was a dead rubber. There's nothing dead about it."
Saturday's match will be the first time David Warner and Steve Smith would face South Africa since they were banned for their roles in ball-tampering scandal during the infamous Test in Cape Town last year.
"There's no way we'll ever get complacent," said former Australia opener Langer. "Not with what's happened the last 12 months. We're playing good cricket, so we want to continue the momentum of winning going forward."
Langer has no expectations as to regarding the extra nerves involved despite what happened when the two sides met each other in Cape Town last year.
"I don't think so. They got a good taste of what they were going to expect from the moment we turned up in England," said Langer.
"This game is significant for a lot of our players, but we've just got to take all the emotion out of it.
"We're here to take the two points, keep the winning momentum going forward and for those guys this is just another exciting game of World Cup cricket for them."
Langer said Australia would come with full force against South Africa, meaning that pacemen Mitchell Starc and Pat Cummins would play despite the contest termed as dead rubber.
"I know Mitch and Pat definitely don't want to miss this game," he said.