A shock defeat for the All Blacks to the Wallabies in Perth on Saturday night will be a double blow for the World Cup winners.
If Steve Hansen's men fall to Australia in the opening Bledisloe Cup test it will mean that they will give up the top ranking inWorld Rugby to Wales, along with most likely the Rugby Championship.
Following the 16-16 draw to South Africa in Wellington, the All Blacks now hold a 1.58 point lead in the rankings over Wales. A loss in Perth would see the All Blacks drop by 1.66 points and into second spot, according to Wales Online.
However it could only be shortlived in Wales don't beat England at Twickenham on Monday morning NZT in the first of two tests dubbed as 'warm-ups' ahead of the World Cup.
Last month Hansen said the rankings mean nothing ahead of a World Cup.
"World ranking is an outcome of what you do so it has nothing to do with the World Cup because you don't win the World Cup if you're the number one team," Hansen following his side's tight win over Argentina.
He says they've shown that many times, particularly in 2007 when they were entered number one and exited in the quarter-finals.
The All Blacks have been on top spot for almost a decade. They moved to number one on November 16, 2009, taking the spot from the Springboks after South Africa beat New Zealand three straight times earlier that season.
The rugby ranking system was brought in by World Rugby just before the 2003 World Cup. Since then the All Blacks have held the top spot for more than 13 years.
World Rugby rankings 1 - All Blacks - 91.54 2 - Wales - 89.96 3 - Ireland - 88.69 4 - South Africa - 86.30 5 - England - 86.27 6 - Australia - 81.91 7 - Scotland - 80.17 8 - France - 79.42 9 - Fiji - 76.98 10 - Argentina - 76.81
