Australia were 141 for five at tea, still 162 behind South Africa's first innings total of 303.

The visitors' troubles started with the first ball of their innings when Langer, playing in his 100th Test, ducked into a bouncer and suffered a blow on the right earpiece. He was forced to retire hurt and taken to hospital for a scan.

In his next over, Ntini had Matthew Hayden caught at gully.

There was a frenetic stand between captain Ricky Ponting and Damien Martyn, who posted a half-century partnership in just 26 minutes off 38 balls, but it was broken by Ntini when Martyn mistimed a pull and was caught at mid-on.

The fast bowler claimed the key wicket of Ponting, who was caught at third slip, and trapped Andrew Symonds leg before wicket.

Ntini took four for 52 in a ten-over opening spell either side of lunch.

Australia suffered another blow when Adam Gilchrist top-edged a pull against Andre Nel and was caught at deep midwicket.

Australia's hopes rested with Michael Hussey, who was unbeaten on 34 at tea. There was no word on when Langer would return to the ground or whether he would be able to bat.

South Africa added 65 runs for the loss of their remaining four wickets Saturday, mainly through an attacking innings of 43 by Nicky Boje.

Australia took the second new ball seven balls into the day and almost immediately claimed the wicket of Shaun Pollock, smartly caught by Australian captain Ricky Ponting at second slip off Stuart Clark.

Ashwell Prince, who held the South African innings together on the first day, took his score from 79 to 93 in just over an hour of batting as he and Boje added 34 for the eighth wicket. But he was forced onto the back foot by a delivery from Brett Lee which he edged to Langer at second slip.