Harris, Johnson tighten Australia's grip
Australia 494 for 7 dec and 27 for 0 (Warner 25*, Rogers 1*) lead South Africa 287 (du Plessis 67, Petersen 53, Johnson 4-42, Harris 3-63) by 234 runs
Scorecard and ball-by-ball details
This series was billed as the showdown of the two best pace attacks in the world and on day three in Cape Town, Ryan Harris and Mitchell Johnson bowled Australia into a position from which they could hope to claim the match and the series. Hurt by Dale Steyn's hamstring injury, South Africa failed to bowl Australia out the first time; led by the intent and intensity of Harris and Johnson, Australia skittled South Africa in less than a day.
It left the Test tantalisingly poised with two days to play. Michael Clarke chose not to enforce the follow-on after South Africa were dismissed 207 runs behind - he did not want to bat last on this surface. But nor is he the kind of man who will die wondering; with a series on the line, Clarke can be expected to declare early enough on day four to give his bowlers plenty of time to skittle South Africa a second time. If one day was enough in the first innings, he will hope one and a half is enough in the second.
By stumps, Australia's lead was 234 runs as the openers moved without drama to 27 for 0 - David Warner was on 25 and Chris Rogers had 1. It is the kind of scenario in which Warner has often thrived in recent times and if he motors along on the fourth morning, Clarke might just call his men in earlier than expected. Whatever the case, South Africa will need a more sturdy batting display than they delivered on day three, when they were dismissed for 287.
It was notable that Australia's first five partnerships in the first innings were all worth more than 50, and that only two in South Africa's entire innings reached that level. Alviro Petersen made a quick fifty at the top of the order, Faf du Plessis tried to recall his Adelaide fight with 67 and there was some late resistance from Vernon Philander and Steyn, but Harris, Johnson and their colleagues were so unrelenting that sustained defiance was impossible.
Johnson finished with 4 for 42 but it was Harris, due for knee surgery after this Test, who really delivered for his captain. Earlier in the series, Harris had looked distinctly fatigable but here he was unflagging, sending down 22 overs including nine maidens on his way to 3 for 63. James Pattinson offered lively pace and picked up two wickets and only a 95-run stand between du Plessis and Philander looked like causing Australia any real problems.
There was seam movement, there was reverse swing and there was the occasional bit of roughing up, like when Petersen was struck on the arm at 150kph by Johnson just before losing his wicket, or when Johnson banged in a bouncer that pinpointed the badge on Steyn's helmet. Mostly, though, it was the movement and persistent lines that did the trick, and the tone was set by the early loss of Graeme Smith for 5 after Clarke declared on Australia's overnight total of 494 for 7.
Smith tried to close the face and work Harris to leg but the ball angled across him off the seam and his edge behind was taken by Haddin. That was a regulation take for Haddin, but the same could not be said of his effort to get rid of Dean Elgar for 11. Pattinson moved a ball back in to Elgar at 145kph and an inside edge flew over the stumps and was brilliantly taken by Haddin diving full stretch to his right.
That left South Africa at 42 for 2 and relying on Petersen and Amla to rebuild. Petersen was far more effective than in the first Test in Centurion and regularly walked across his stumps to work the ball to leg. His aggressive mindset brought him eight fours and he reached his half-century from 50 balls, but Johnson's pace also provided him with the odd nervous moment.
Johnson eventually had his man when he banged one in at the ribs of Petersen, who on 53 tickled a catch off the gloves down leg and was taken by Haddin. Amla remained at the crease, though, and was good at milking the runs off Lyon, while also providing some soothing sights for the South African fans, including a sublime drive through cover-point for four off Harris. But Amla went for one drive too many against Harris and was bowled for 38 when a delivery nipped back in beautifully off the seam.
AB de Villiers drove away from his body and edged to second slip off Johnson for 14, before JP Duminy was set up wonderfully by Harris, who gave him a couple of inswingers on the pads and then angled one across him that drew an edge behind. Australia missed the chance to get through South Africa a little quicker when Haddin muffed a straightforward stumping opportunity off Nathan Lyon when du Plessis had 30, and it was one of three chances of varying degrees of difficulty for du Plessis.
A couple of lovely clips through leg off Lyon brought du Plessis his half-century but on 67 he pushed at Johnson and was sharply taken by Warner low to the ground at gully. Shane Watson bowled Kyle Abbott and then snared two catches at slip to finish the innings, Steyn caught off Johnson for 28 and Morne Morkel off Pattinson for 7, and Philander walked off unbeaten on 37, which occupied 107 balls and more than three hours.
It was the kind of fight that South Africa's batsmen will need to show in the second innings. It may be hard to see a realistic path to victory for South Africa, but denying Australia a series win is still a goal worth pursuing.
Brydon Coverdale is an assistant editor at ESPNcricinfo. He tweets here