Australia need a record run-chase or biblical rain in Port Elizabeth if they're to prevent South Africa posting a victory that would square the three-test series.
The Proteas' dominance was never called into question on day three of the second Test, when they restricted Australia to a total of 246 and reached 4-192 at stumps to boast a 369-run lead.
The visitors will be chasing well in excess of the 273 scored by South Africa in 1962, the highest fourth-innings total recorded at St George's Park.
In all likelihood it will be higher than 418, the world-record mark West Indies chased down in 2003.
The timing of Graeme Smith's likely declaration on Sunday will be key, because the fluent knock of Hashim Amla suggests the remaining six wickets won't come quickly.
Amla, batting after dislocating his finger in the field, returned to form in style with an unbeaten 93 that came at a good clip.
Brad Haddin put down a tough chance when Amla was on 83, but the damage had been done.
Mitchell Johnson was menacing in an opening spell of 1-20 from four overs, and both he and Michael Clarke exchanged terse words with Smith.
Smith (14) was out to Johnson for the eighth time in his Test career, chopping one onto the stumps.
Peter Siddle had both Dean Elgar and Faf du Plessis caught behind and Johnson removed AB de Villiers (29), but South Africa needed to suffer an almighty collapse to give Australia a genuine sniff of victory and it didn't happen.
Predicted showers on Monday may be on Smith's mind, but he will feel confident about the prospect of rolling Australia quickly given their first innings lasted 57 overs.
It would have been even shorter had David Warner (70), Steve Smith (49), Haddin (nine) and Nathan Lyon (15) not been dropped.
Smith was given the most unforgivable reprieve, 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, third umpire Aleem Dar overturning Richard Illingworth's not-out verdict shortly after lunch despite there being no overwhelming evidence of an edge.
The collapse was all the more costly given South Africa will be a bowler down.
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 that starts on Saturday.
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 day two, and will need to be managed well if they're to come up for the next clash.
Scoreboard at stumps on the third day of the second cricket test between South Africa and Australia at St George's Park:
First Innings 423
First Innings (Overnight 112-4)
Chris Rogers lbw b Philander 5
David Warner c Smith b Philander 70
Alex Doolan c De Villiers b Parnell 8
Shaun Marsh c De Villiers b Parnell 0
Michael Clarke c Elgar b Philander 19
Nathan Lyon b Morkel 15
Steve Smith c De Villiers b Morkel 49
Brad Haddin b Steyn 9
Mitchell Johnson b Duminy 27
Ryan Harris c Du Plessis b Morkel 26
Peter Siddle not out 11
Extras (4lb, 2b, 1w) 7
Fall of wickets: 1-7, 2-41, 3-41, 4-81, 5-120, 6-128, 7-168, 8-205, 9-209.
Bowling: Dale Steyn 13-3-55-1, Vernon Philander 13-0-68-3, Morne Morkel 17-0-63-3, Wayne Parnell 8.3-2-31-2, Dean Elgar 0.3-0-1-0, JP Duminy 5-0-24-1.
Graeme Smith b Johnson 14
Dean Elgar c Haddin b Siddle 16
Hashim Amla not out 93
Faf du Plessis c Haddin b Siddle 24
AB de Villiers c Haddin b Johnson 29
Quinton de Kock not out 9
Extras (2b, 5lb) 7
Total (for 4 wickets) 192
Fall of wickets: 1-20, 2-42, 3-112, 4-167.
Bowling: Mitchell Johnson 12-0-48-2, Ryan Harris 10-1-53-0, Nathan Lyon 12-2-31-0, Peter Siddle 13-2-53-2.
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