Marco Jansen landed Australia in soup with a five-wicket haul that accelerated their collapse on Day 4 after Temba Bavuma, and Jansen himself, tailored South Africa's steely comeback on the previous day. It took just 38.3 overs for Australia to fold for 99 in reply to South Africa's 428/9 declared, and having to bat again with the threat of a big defeat looming over them. Marnus Labuschagne and Travis Head pushed back with a show of defiance but South Africa managed to crack that too, leaving the visitors at 156/4 at stumps. The morning session belonged to Jansen. He started with a wicket first ball, taking out Scott Boland and then removed Head too. Labuschagne tried to stick around but Simon Harmer took a one-handed screamer diving to his left at gully to dismiss him. Steve Smith and Matt Renshaw dug in for the next 15-odd overs and seemed set to take Australia to Lunch without further damage but Jansen delivered a double-wicket over where he dismissed Renshaw and Alex Carey. The collapse, on the other hand, did not occur again. Labuschagne and Head joined forces to push back. Together, they batted for nearly 30 overs, totaling 92 runs. Labuschagne even escaped a narrow LBW call and thanked the heavens as a review ruled against the bowling side. But he followed that up with the questionable decision of giving Harmer the charge and miscuing a big shot. Jansen, who could do no wrong in this fixture, covered a lot of real estate running backwards and completed a catch to put the brakes on Australia's resilience. Renshaw tried to kickstart another gritty alliance with Head but Rabada cleaned him up with a ball from round the stumps to which the batter offered judgement. Given Australia's predicament, Head was moving along at the other end at a refreshingly even pace, but his batting partners were unable to keep up or stay put. After Harmer's leg got caught, Beau Webster was the next one to walk back. Boland wouldn't have imagined starting and ending the day in the middle with a bat in hand, but that's how it panned out for his team as the Test swung fiercely in South Africa's direction. Head scored a fifty, had a subdued acknowledgement of it, and walked off at stumps on 87* off 138. On Day 5, when Australia will be 170 runs behind and South Africa will be focused on bowling six good deliveries for series parity, he will play a bigger role.