Mitchell Starc puts Australia in total control
Mitchell Starc produced reverse swing of the highest order to bowl South Africa out for 162 at the end of the second day.
The left-arm paceman took 5/34 in 10.4 overs to give Australia a potentially match winning lead of 189.
Only AB de Villiers stood firm with an unbeaten 71 and one that'll be in vain in the context of the game.
The deficit is a hefty one and it will settle the outcome of the game considering how poorly South Africa batted in the evening session.
In the bigger scheme of things, should the hosts lose this test, they'll look at the spinelessness that pervaded their batting in the session as the key factor.
South Africa lost seven wickets for 107 runs in 32.5 overs. That's as abject a collapse as it can be.
Villiers stood with his torso above the parapet and absorbed everything that came his way. A first test century since January 2015 sadly eluded him but it was not of his own doing.
Their task was a simple one; minimise the damage while trying to avoid the follow-on. In getting to the promised land of 151, they lost six wickets.
The most recent of those was the hopelessly out-of-form Quinton de Kock, who played around a Nathan Lyon arm ball.
Australia bowled intelligently and when necessary, with pace and serious hostility. They also had the element of left-arm fast reverse swing from Starc that swung the day in their favour decisively.
With Lyon there to trouble the top-order lefties that he got rid of, Starc broke the spine of the batting with high quality reverse swing.
Faf du Plessis (15), Theunis de Bruyn (six) and Vernon Philander (eight) feathered catches to Tim Paine.
Du Plessis played away from his body but the next two were out to deliveries that would have pinned them leg before or castled them.
Keshav Maharaj had no response to a Josh Hazlewood delivery that detonated his off-stump and pretty much stunted South Africa.
The tail folded quickly in the face of a furiously accurate Starc with Kagiso Rabada (three) and Morne Morkel (nought) having no response to balls that honed in on their stumps.