Australia's stunning fall from super-team to aging strugglers was confirmed in Melbourne today as South Africa sealed a historic nine-wicket victory.

After a decade and a half of domination, Australia have finally been beaten in a home Test series - and if they lose again in Sydney next week to suffer a 3-0 whitewash then Ricky Ponting's side will slide from first to third in the official world rankings.

But regardless of how the ladder looks in the early days of 2009, even the most myopic Aussie supporter must now accept that both South Africa and India have moved ahead where it matters most - on the field - leaving Ponting's wounded champions to start a rebuilding process which should leave them vulnerable for summer's Ashes battle.

South Africa had never won a Test series in Australia, while their hosts were protecting an unbeaten home record stretching back to 1993. Two remarkable matches have changed all that, however.

In Perth, Australia looked untouchable when they set Graeme Smith's team 414 for victory. But, far from being swept away, South Africa cruised to victory. Then, in Melbourne, Ponting's side were in charge again, only for the visitors to crush their spirit with an astonishing ninth-wicket stand of 180 between rookie batsman JP Duminy and fast bowler Dale Steyn.

For years, under the leadership of Allan Border, Mark Taylor, Steve Waugh and Ponting, when Australia had their foot on an opponent's throat in a match that mattered they did not stop pressing until victory had been achieved. Now they are fallible and riddled with doubt.

"We had our opportunities in the first two Tests but when the big moments came up we weren't good enough to put the nails in the coffin," Ponting admitted today as South Africa celebrated at the MCG.

"We are in that transitional phase, there's no hiding that. Especially now being 2-0 against the South Africans it's not so much a reality check as a bit of an awakening for us to actually sit back and look at a lot of the things they've done well and try to learn."

In fairness to a fading side, Australia have over-achieved in extending their era of domination by nearly two more years.

Losing champion fast bowler Glenn McGrath, superstar leg-spinner Shane Warne and prolific opening bat Justin Langer immediately after completing a 5-0 whitewashing of England a couple of winters ago should have brought Australia straight back to the pack. Instead, under Ponting's leadership, they have somehow clung on to their cloak of invincibility - until India ripped it in half by winning 2-0 during November and then South Africa snatched it clean away in Perth and Melbourne.

The inquests had begun Down Under even before Smith's team completed their run-chase today. The visitors, 30 without loss overnight, lost only their captain, for a fluent 75, before reaching the modest victory target of 183.

Now the knives are out for 37-year-old opener Matthew Hayden, whose career appears to be in terminal decline, while fingers have also been pointed at Ponting's captaincy. And, as always seems to happen when a team is down, injuries make the picture look even gloomier for Australia.

Fast bowler Brett Lee is struggling with a foot problem and all-rounders Andrew Symonds and Shane Watson face surgery on knee and back problems respectively. But Australia's woes should not detract from South Africa's sparkling triumph. They had a two-year plan to rise to the summit of Test cricket and they have now won nine of their last 10 series - drawing the other in India. "This is up there with winning the World Cup, if not better," said all-rounder Jacques Kallis.

The next task for South Africa, with their impressive batting line-up and enviable battery of fast bowlers, is to go from strength to strength.

As for Australia, they have the Sydney Test and then a return series in South Africa to prepare themselves for an Ashes showdown which could turn out to be a contest between the sides ranked third and sixth in the world.

That may be a bitter pill for Ponting's men to swallow, but history suggests they will still take some beating when they come over here - whatever the league table says.