Centurion Michael Clarke was cautious, Steve Smith audacious and, by lunch on day two of the Test series decider, Australia had batted South Africa out of the contest.

The tourists were 4-434 at Sunday’s meal break, Clarke (137 not out) and Smith (84) having put on a stand of 184 in windswept Cape Town.

It is near impossible to see the Proteas battling back to level footing in this contest, especially with Dale Steyn nursing a hamstring strain and not expected to bowl again in the match.

Predicted afternoon showers loom as the only respite for the hosts’ weary attack, with Vernon Philander, Morne Morkel and Kyle Abbott having bowled a combined 71.5 overs already.

None triggers trepidation like Steyn, and none has made a breakthrough since Steyn went off the park in the 40th over on Saturday.

The Proteas maintained their rate of one wicket a session, Smith chopping a mediocre ball from part-time spinner Dean Elgar onto the stumps.

Australia resumed on 3-331 with Clarke donning a bandaged arm and a borrowed protective guard after copping a series of blows from Morkel in a brutal short-pitched assault on day one.

The stoic skipper needed eight runs to complete his 27th Test ton and join former captain Allan Border on the all-time list of Australian century makers.

It proved a nervous 47-minute wait for the 32-year-old, who faced 25 balls as eight overs ticked past while he was on 99.

During that period, Smith was nearly run out and Clarke left a series of deliveries that went within millimetres of hitting the stumps.

But he finally brought up the century with a cover drive off Philander that sent the ball whistling to the rope.

Smith was the perfect free-spirit foil to Clarke, unleashing two incredible sixes.

The 24-year-old lofted a length ball from Philander straight back over his head then, the next over, popped a Morkel delivery over the covers and past the rope in similar pitching-wedge fashion.

Shane Watson (21 not out) launched a six in the 114th and final over before lunch, with long-off Philander picking the ball up late and not attempting to catch it.

Watson’s first ball featured a confident lbw shout and review from Graeme Smith, but replays showed it hit the bat first.

The fit-again allrounder, who alongside James Pattinson was drafted into the XI that lost in Port Elizabeth, was almost run out the next delivery but AB de Villiers erred in his attempt to dislodge the bails after reeling in a loose return.