South Africa on the ropes against Australia

PERTH: Australia's second-string pace attack stunned South Africa on the opening day of the third and final Test at the WACA Ground on Friday.

After winning the toss and electing to bat, the Proteas were struggling at 141 for seven at tea in a match that will decide the top-ranked nation in Test cricket.

Second Test hero Faf du Plessis was again fighting to revive the South African cause and was on 39, with Vernon Philander on four.

Australia were forced to completely revamp their pace attack for the match, with their three pacemen from the drawn second Test in Adelaide -- Peter Siddle, Ben Hilfenhaus and James Pattinson -- all ruled out.

Left-armer Mitchell Johnson was recalled for his first Test in 12 months, Mitchell Starc was promoted after being 12th man for the first two matches in the series, and John Hastings was handed his Test debut.

All were in the wickets as they decimated the South African top order, the visitors at one stage losing five wickets for 14 runs either side of lunch as they slumped to 75-6.

It was the returning Shane Watson (1-14) who claimed the first wicket, having Graeme Smith caught at first slip by Michael Clarke for 16.

Watson made a welcome return from a calf injury, having missed Australia's last eight home Tests, finding a thick outside edge from Smith to remove the Proteas skipper.

Just before lunch, Starc (2-47) struck two telling blows as the day took a sharp turn.

Starc removed opener Alviro Petersen (30) when he bowled the right-hander with a full delivery and then found a way through the defence of Kallis (2), who overcame a hamstring injury to take his place in the match, with a similar ball.

Already struggling at 63-3 at lunch, the Proteas crumbled after the resumption, with Hashim Amla (11), AB de Villiers (4) and debutant Dean Elgar (0) all falling in quick succession.

Amla was run out by a brilliant direct hit from David Warner in covers, de Villiers became Hastings' first Test scalp when caught at first slip by Clarke and Elgar gave Johnson a well-deserved first wicket when he was caught behind.

Just before tea, spinner Nathan Lyon (1-13) had Robin Peterson caught behind for 31 to end a 57-run partnership with du Plessis.