Australia could surrender their second place in the IRB World Rankings if they suffer a second loss to New Zealand in as many weeks in The Rugby Championship on Saturday.
The Wallabies, beaten 27-19 by the world champions in Sydney last weekend, will fall to third if South Africa also beat Argentina by more than 15 points later that day in Mendoza.
That scenario will be enough to see South Africa return to second for the first time since they lost to Australia in the Rugby World Cup 2011 quarter finals, albeit only by two hundredths.
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A smaller margin of victory for South Africa will see Australia cling onto second place with the two sides to meet in round three of The Rugby Championship in Perth on 8 September.
New Zealand can only gain a maximum of 0.14 rating points with an emphatic win over the Wallabies at Eden Park, the world champions being at home and now 6.1 points above Australia.
A win, though, would ensure the Bledisloe Cup remains in New Zealand hands for the 10th year in a row and preserve their unbeaten run against Australia at Eden Park, which dates back to 1986.
On the other hand, New Zealand’s cushion at the top could be slashed to less than four tenths if an Australia side without star flanker and captain David Pocock can avenge their loss in Sydney.
South Africa cannot slip from third if they suffer a first loss to Argentina, although their advantage over England, the leading northern hemisphere nation, could shrink to just three hundredths.
Argentina, if they can create history at the Estadio Malvinas Argentinas by defeating a Springbok side playing a first Test in the country since 2005, will climb one place to seventh in the rankings, swapping places with Ireland.
They cannot fall from eighth with defeat by the Springboks, although a repeat of the 27-6 loss on their Rugby Championship debut will cut their advantage over Scotland to just two hundredths.
This could prove costly for Argentina come the Rugby World Cup 2015 Pool Allocation Draw in London on 3 December as being ranked ninth would leave Argentina in band three and facing a tougher challenge at England 2015.
The IRB World Rankings update every Monday at 12:00 UK time.