Johannesburg: Australia's ball-tampering scandal came back to bite them when three replacement batsmen failed on a disastrous day for the tourists in the fourth Test against South Africa at the Wanderers Stadium on Saturday.

South Africa moved closer to a series win as Australia slumped to 110 for six at the end of the second day in reply to the imposing first-innings total of 488 made by the hosts.

South Africa, leading the series 2-1, need only to draw to beat Australia in a home series for the first time since 1969/70.

Opening batsmen Joe Burns and Matt Renshaw were out for four and eight respectively while Peter Handscomb was out first ball for nought to leave Australia reeling at 38 for three.

The trio were playing in place of Cameron Bancroft, David Warner and captain Steve Smith, who were all banned and sent home in disgrace after the ball-tampering scandal which rocked the third Test in Cape Town last weekend.

“Putting three guys into a Test match, two have come from Australia and one hasn’t played in a game for a while, was always going to be a little bit tough,” said Australian bowling coach David Saker.

He added: “We’ve tried to really care for each other this week. We’re realists and we’re going to go out and try and play as well as we can, to put in a performance that the Australian public and our group are proud of. 

"So far it hasn’t happened but the effort has been there. There’s no doubt in the dressing room that the guys are trying their hardest. It just hasn’t worked in this game.”

Usman Khawaja made a stroke-filled 53 as he and Shaun Marsh delayed South Africa's progress with a fourth-wicket stand of 52.

But wicketkeeper Quinton de Kock, standing up to the wicket, made an outstanding leg-side catch off the bowling of Vernon Philander to dismiss Khawaja.

Philander finished the day with three for 17 off 12 overs.

Shaun Marsh survived a stumping chance off Keshav Maharaj in the over after Khawaja's dismissal but both Marsh brothers fell before the close to leave Australia with a monumental task over the remaining three days.

Mitchell Marsh edged an extravagant drive against Morne Morkel into his stumps and three balls later Shaun Marsh was caught at slip by AB de Villiers off Maharaj.

Tricky period: It was South Africa's day from the time Temba Bavuma and De Kock weathered a tricky period against a ball that was almost new after resuming at 313 for six.

Bavuma made 95 not out and shared partnerships of 85 with De Kock (39) and 76 with Maharaj, who hit a cavalier career-best 45 off 51 balls.

Bavuma was within sight of his second Test century when Australian fast bowler Pat Cummins took two wickets with successive balls to finish off the innings.

Cummins was easily Australia's most impressive bowler, finishing with five for 83.

New opening batsmen Burns and Renshaw, who only arrived on Wednesday night, did not last long.

Burns was caught by a diving Faf du Plessis at second slip off Kagiso Rabada, while the other two fell off successive balls from Philander. 

Renshaw was caught behind, quickly followed by Handscomb, who was bowled off an inside edge as he tried to withdraw his bat from a lifting delivery. 

Earlier in Sydney, deposed vice-captain Warner said he realised he may never play for Australia again as he tearfully apologised over the ball-tampering scandal.

'Regret decision': The usually pugnacious batsman, 31, repeatedly struggled to talk and tears ran down his face as he apologised to fans, team-mates, his family and the Australian public.

But he also evaded questions about whether the plot was his idea, whether it was the first time, who else was aware of it and whether he had been made a scapegoat.

Warner said: "I have made a decision which I will regret for as long as I live."

Warner's appearance comes after similar heartfelt apologies from opening batsman Bancroft and Smith, who broke down when he faced the media on Thursday.

Coach Darren Lehmann, convinced to step down after seeing the anguished statements from Bancroft and Smith, was also tearful as he announced his resignation in Johannesburg on the eve of the fourth Test.

Smith and Warner were banned from international and domestic cricket for a year and Bancroft was suspended for nine months after the incident during the third Test in Cape Town.

Bancroft was caught on camera trying to use sandpaper to alter the ball, an offence which triggered an outpouring of criticism from home and abroad against the hard-nosed Australian team.