South Africa looked set for a big total after a century opening stand, but two collapses in one innings handed Australia control of the deciding Test.
Century opening stand sets the platform
Pat Cummins won the toss and chose to bowl first in Cape Town. Aiden Markram and Marcus Ackerman gave South Africa a strong start, reaching 140 without loss at the end of the first session, with both batters past fifty.
Ackerman, batting at more than a run a ball, missed his maiden Test century by five runs, stumped off Nathan Lyon for 95 off 94 balls, with 12 fours and two sixes. Markram followed for 78, the second wicket to fall at 202.
First collapse, five wickets for 30 runs
South Africa then lost four more wickets while adding just 30 runs, sliding from 202 for 1 to 232 for 6. Captain Temba Bavuma and Wiaan Mulder were both dismissed without scoring.
The middle order could not stop the slide, and Australia's bowlers turned a position of comfort for the hosts into a contest again.
Recovery, then a second collapse
Ryan Rickelton and Marco Jansen rebuilt with a 95-run partnership off 144 balls, taking South Africa to 327 for 6. But the recovery ended in a rush, as the last four wickets fell for just two runs.
Starc struck four times within six balls. He trapped Rickelton leg before wicket for 42, bowled Jansen for 52, and then removed Gerald Coetzee and Kagiso Rabada, neither of whom scored.
Bowling figures and team changes
Starc finished with six wickets, taking his last four with the second new ball. Lyon took two wickets, while Josh Hazlewood and Cooper Connolly took one each.
Australia made four changes to their playing eleven, with Beau Webster, Nic Maddinson, Scott Boland and Steve Smith all missing out. South Africa made one change, with Anrich Nortje ruled out through injury.
