South Africa's task goes from impossible to improbable
Australia will be unnerved by fitness concerns surrounding their strike bowlers Peter Siddle and Mitchell Johnson. Both have shouldered a mountainous workload over the past fortnight, and were clearly battling injury and fatigue for much of the fourth day. The relatively inoffensive trio of Andrew McDonald, Marcus North and Simon Katich were called upon to bowl the final 11 overs to Kallis and de Villiers before stumps, and Ricky Ponting will be hoping his pacemen have enough in reserve to mount one, final assault with the second new ball on Tuesday morning.
Siddle bowled with pace and aggression to claim the only two South African wickets to fall but, concerningly, hobbled from the field with a foot injury prior to the tea break. Johnson, meanwhile, clutched at his left hamstring after retrieving a ball in the outfield late in the second session, and may well be feeling the cumulative effect of bowling a back-breaking 722.5 overs since the beginning of 2008 - by far the most of any paceman in Test cricket.
Siddle returned to the field after having the foot restrapped, and team physiotherapist Alex Kountouris stood behind the fine-leg boundary rope to confer with him during his final five-over spell. The medico's presence hinted at the concerns within the Australian camp, given Siddle's recent history of missing the majority of the limited-overs series in Australia, and several training sessions last week, due to a stress reaction to his left foot.
Prior to leaving the field, Siddle had led the Australian attack with aplomb. The right-armer removed Neil McKenzie caught behind after the lunch break, and would have had Kallis with his next delivery had North displayed sharper reflexes at first slip. Siddle roared to the heavens in frustration as the ball spilled from North's right hand, but the paceman exacted a measure of revenge later in the session with the wicket of Hashim Amla.
In a devilish over, Amla was struck a glancing blow to the upper body and shouldered arms to a delivery that cut back within millimetres of his off stump before eventually chasing a wider ball that flew to Ponting at second slip.
The Australians could not make another breakthrough before stumps as Kallis, making the most of his second life, and de Villiers displayed tremendous tenacity and resolve to grind out an unbroken century stand in what history would suggest is a hopeless cause. But with two-and-a-half sessions negotiated, a successful 414 run chase in Perth still fresh in the memory and Graeme Smith presumably willing to again don the cape and the pads if the Test were on the line, a match-saving effort cannot be discounted entirely.
Earlier, Ponting sought to turn the screws on his opponents by batting into the fourth morning before eventually declaring at 331 for 5 - setting a target that, if achieved, would eclipse the previous successful fourth innings chase by a cool 128 runs. The session was again dominated by the flashing blade of Phillip Hughes, who reached his maiden Test 150 with a dramatic straight six off Dale Steyn, and prompted more melancholy among the hometown spectators at Kingsmead.
Few were left guessing as to Hughes' intentions on Monday when he drove Makhaya Ntini's first offering of the day to the boundary. The rookie opener was dropped by Mark Boucher in Steyn's next over, then compounded the error by swatting Steyn into the stands to reach 150.
Hughes treated the remainder of his innings as he would a Twenty20 match, stepping extravagantly to the leg side ahead of every delivery and swiping with tremendous power, if not grace. The high-risk, high-yield strategy eventually prompted his downfall, however, when he thrashed an Ntini offering to a roving Morne Morkel on the third-man boundary. In all, he had scored 24 runs from 25 deliveries on the fourth morning to take his series tally to a stunning 350 at 87.50. No other batsman in the series has passed the 200 mark.
Ponting eventually declared after North was dismissed for a duck to a sharp, one-handed catch by de Villiers off the bowling of Steyn. The long climb for South Africa had begun.
Alex Brown is deputy editor of Cricinfo