A batting collapse on day 2 of the third Test against South Africa at the WACA shone the spotlight on the lack of stability in the Australian top order.

Australia was all out for 163 and trails South Africa by 62 runs in the first innings.

Up to now, the in-form skipper had come to the crease this series with Australia in trouble, only to set the ship straight.

Clarke had then been joined by Mike Hussey and together the pair routinely smashed Australia into the advantage.

However, in the first innings in Perth, South Africa sent the dynamic duo packing for 17 runs.

Clarke made five and Hussey 12, leaving Australia reeling at 7-100.

Openers Ed Cowan and David Warner took it in turns to make hundreds in Brisbane and Adelaide, but otherwise Australia's top three have left the middle order exposed far too easily.

Rob Quiney failed at No.3 in his only two Tests at the Gabba and Adelaide, and his replacement, Shane Watson, made 10 at the WACA.

Retiring great Ricky Ponting has made 24 runs in four innings this summer and Australia must find a reliable new No.4.

Clarke and Hussey have been in special form this summer, but yesterday proved that even the superstars of the team can't be relied on every single time.

So far this series, Clarke, batting at No.5, has always come in with less than 100 on the board.

In Brisbane he made 259 not out after coming in at 3-40.

In the first innings in Adelaide he came in at 3-55 and made 230.

The second innings he arrived at 3-91 and, despite only making

38, it was all that was required.

At the WACA, Clarke was in at 4-35, after Nathan Lyon had come in earlier as a nightwatchman.

Australia needed its saviour again but Dale Steyn quickly put paid to that.It's a far cry from the golden period of Australian cricket when top order players such as Matt Hayden, Justin Langer and Ponting protected the middle order from the new ball more often than not.