Australia struck twice in the space of 71 minutes, but South Africa remain in the box seat to complete a victory in Port Elizabeth that would square the three-Test series.

The Proteas restricted Australia to a total of 246, then reached 2-58 to boast a 235-run lead at tea on day three.

Mitchell Johnson was menacing in an opening spell of 1-20 from four overs on Saturday, but Graeme Smith was the only batsman to fall to the fiery left-armer.

Peter Siddle picked up his first wicket of the match, Dean Elgar caught behind for 16.

But South Africa need to suffer an almighty collapse to give Australia a sniff in this match and Hashim Amla looks in good touch.

Amla (24 not out) and Faf du Plessis (one not out) are not prone to handing their wickets over easily.

In addition, Australia’s pace trio have already been overworked in the game.

Johnson, Siddle and Ryan Harris bowled a combined 86 overs in South Africa’s first innings, which only wrapped up in the final session of Friday.

Nathan Lyon, who finished with figures of 5-130 from 46 overs in the first dig, will again have to bowl some marathon spells.

Predicted showers on Monday loom as the biggest obstacle in South Africa’s search for a win, but the hosts have scored quickly in the 15 overs of their second innings.

And given the way Australia’s first innings lasted 57 overs, they will need a markedly improved effort with the bat for this match to reach a fifth day.

Australia’s total would have been a lot lower had David Warner (70), Steve Smith (49), Brad Haddin (nine) and Nathan Lyon (15) not been dropped.

Smith was given the most unforgivable reprieve of the four, substitute fielder Robin Peterson grassing a regular catch when he was on 24.

The 24-year-old was also the most unlucky to lose his wicket, with third umpire Aleem Dar overturning Richard Illingworth’s not-out verdict shortly after lunch despite there being no overwhelming evidence of an edge on Hotspot and Snicko.

Australia enjoyed a minor victory when Ryan Harris heaved a short ball from Vernon Philander over the mid-wicket fence to pass the follow-on mark.

The collapse was all the more costly given South Africa will be a bowler down for the rest of the match.

Wayne Parnell, playing his first Test in four years, limped off the field midway through his ninth over with a groin strain and is in doubt for the likely series decider in Cape Town.