The top spot in the International Rugby Board's world rankings will be at stake when New Zealand tackle South Africa in Auckland on Saturday night.
The All Blacks have been the No.1 side in the world since November 2009 and are undefeated since their loss to England at the end of last year but the Springboks' recent strong run of form has brought them to within striking range ahead of their Eden Park showdown where a victory for the visitors would see the sides seap places in the ranking.
New Zealand, who have occupied top spot for 82% of the time since the rankings were introduced in October 2003, currently have a 2.7 rating point cushion over South Africa at the halfway stage of their Rugby Championship title defence.
However, if South Africa can end New Zealand's run of 30 consecutive victories at Eden Park then that deficit will be turned into at least a 0.44 point advantage. If Heyneke Meyer's men can win by more than 15 points then South Africa would enjoy a cushion of just over two points.
Their first loss of this year's Rugby Championship, though, could see South Africa, one of only three sides to occupy the number one spot in the history of the rankings, slip back to nearly four rating points behind New Zealand if the All Blacks were to win by more than 15 points.
IRB World Rankings: (September 9, 2013)
1. (1) New Zealand - 91.64
2. (2) South Africa - 88.94
3. (3) England - 85.76
4. (4) Australia - 83.67
5. (5) France - 81.59
6. (6) Wales - 81.36
7. (7) Samoa - 80.42
8. (8) Ireland - 79.58
9. (9) Scotland - 76.95
10. (10) Argentina - 76.41