Cape Town - Ireland will jump to the top of the World Rugby rankings if they beat England in their Rugby World Cup warm-up clash at Twickenham on Saturday.
Kick-off is at 16:00 SA time.
A win - by any margin - would see the Irish jump from third to first, with Wales dropping to second and New Zealand to third.
The Welsh became the world's No 1 team for the first time on Monday following their 13-6 win over England in Cardiff last weekend.
Meanwhile, a win for England - again by any margin - would see them leap-frog South Africa into fourth spot.
The Springboks moved above England after their 24-18 win over Argentina in Pretoria at the weekend.
Top 20 in the latest World Rugby rankings:
1. Wales 89.43
2. New Zealand 89.40
3. Ireland 88.69
4. South Africa 86.83
5. England 86.79
6. Australia 84.05
7. France 80.58
8. Scotland 79.01
9. Japan 77.21
10. Fiji 76.98
11. Argentina 76.29
12. Georgia 74.42
13. Italy 72.04
14. USA 71.93
15. Tonga 71.49
16. Samoa 69.08
17. Spain 68.15
18. Romania 66.69
19. Uruguay 65.18
20. Russia 64.81
Others:
23. Namibia 61.01
32. Kenya 51.44
33. Zimbabwe 51.42
FULL RANKINGS