Labuschagne's selection has remained the key talking point ahead of the third Test against the Proteas, after his run of innings without a century extended to 47.
Matt Renshaw is expected to open in place of the dropped Nic Maddinson in Cape Town, with Cameron Green to bat in the middle order.
Steve Smith's neck injury could also affect the final team, but Labuschagne is expected to hold his spot regardless ahead of the fit-again Josh Inglis.
The Queenslander has scored between 30 and 49 in six of his past nine innings, while his career average over the past 37 Tests is half what it was in his first 30.
Australia have made no secret of their frustration with that, with Pat Cummins last week admitting .30s "aren't going to win too many matches".
By the same token, Australia do believe Labuschagne is getting through the hard period and batting well, before a psychological issue around the 30s.
"The focus is on hundreds. I don't think I'm in a position to defend the performance," chief selector George Bailey said.
"But in terms of the collective, there's been times where that's helped. And that's the question we keep asking ourselves.
"We're seeing some good things, yes. Is there a block at the moment around 30s? Yes.
"He's still contributing in terms of his ability to get through a number of balls. So it's a decision around what does that look like if it gets through there.
"And what does it look like for the collective ... Is it helping the team get a result?"
Labuschagne's long-time teammate Usman Khawaja also raised similar questions around a potential mental block on Monday.
"He has obviously struggled for a while and I find when things are going that long it is usually mental more than technical," Khawaja said.
"It is very hard to score in this game, even if you are slightly clouded in the mind. I don't envy Marnus.
"He has played some terrific innings over the years for Queensland and Australia. It is hard. It has always been hard.
"I remember this feeling and it is tough. He has obviously struggled of late and that is what cricket does. It is a great leveller."
Asked on Monday whether Labuschagne's crease occupation against Inglis' scoring rates were being weighed up, Cummins' suggested it may be a factor.
"Both have positives to it," he said.
"I think anywhere in the world, batting in the top three is really tough and Marnus is doing the hard work. He is facing quite a lot of balls and getting himself in."
