The Springboks face Wales in Durban this weekend with their number one World Rugby ranking on the line, though a win cannot improve their rating due to the 17.58-point differential between the two sides.
South Africa can only lose the top spot, not extend their lead. A defeat to Wales, paired with a New Zealand victory over Ireland at Eden Park by more than 15 points, would return the All Blacks to number one. Either margin — South Africa's loss or New Zealand's win — needs to exceed 15 points, but both conditions must be met.
Ireland can leapfrog both South Africa and New Zealand into top spot if they beat the All Blacks by more than 15 points while the Springboks also lose by the same margin in Durban. That would mark Ireland's return to number one for the first time since November 2024. A win by any margin over New Zealand, regardless of the Durban result, would at minimum move Ireland above the All Blacks into second. New Zealand, for their part, can close the gap on South Africa to as little as 1.68 rating points with a victory over Ireland that falls short of the 15-point threshold.
Elsewhere in the final southern hemisphere round of the Nations Championship, Australia face an unwanted piece of history. A loss to Italy in Perth by more than 15 points could, under the right combination of results, see the Wallabies drop out of the top 10 for the first time since the World Rugby rankings were introduced in October 2003 — Joe Schmidt's last match in charge. That scenario requires Fiji to beat Scotland and either Japan or Wales to upset France or South Africa respectively. Fiji would also leapfrog Australia into eighth with a first Nations Championship win if the Wallabies lose to the Azzurri.