On a green surface and in damp, overcast conditions, Australia fell to 8-4 and 17-5 after losing the toss. Vernon Philander took 5-21, Kyle Abbott 3-41 and though Steve Smith ended 48 not out, Australia slumped to their lowest home total against the Proteas. South Africa reached 171-5 by the close for a lead of 86 - Hashim Amla hitting 47, while Mitchell Starc has 3-49. The tourists, without injured skipper AB de Villiers and pace spearhead Dale Steyn, already lead the three-Test series 1-0.
Coach Darren Lehmann has voiced concern about Australia's batting lineup after a poor display in which the hosts were bowled out for 85 by South Africa on the first day of the second test in Hobart.
Vernon Philander and Kyle Abbott made full use of the conditions, picking up eight wickets between them to wrap up Australia's innings in less than two-and-a-half hours.
Lehmann, who indicated that radical changes to the team may be needed, was asked by reporters if he thought Australia were in a batting crisis.
"When you get bowled out for 85, it probably is, isn't it?" he said.
Only two Australian batsmen reached double figures, pace bowler Joe Mennie making 10 and skipper Steve Smith a gritty 48 not out.
Lehmann said it was the time the selectors reassessed their options.
"We believe this is the best squad we've got to play. On today's performance you'd say we've got to change," the former left-handed batsman added.
"We had seen it all before, but that didn't make it any easier to believe it was happening again, this time on home soil."
Lehmann said the performance brought back memories of the fourth Ashes test of 2015 when tourists Australia were bowled out for 60 in their first innings by England in Nottingham.
Saturday's debacle represented Australia's second-worst start in a home test when batting first since they lost six wickets for 31 against England in Brisbane in 1978.
Australia's last tour ended in a 3-0 series drubbing by Sri Lanka and they were beaten by 177 runs by South Africa in the first test of the current three-match series.
"Even four tests ago we were number one. Now, we're way away from that," Lehmann added.
Mitchell Starc and Josh Hazlewood picked up two wickets each as South Africa reached 171 for five at stumps.