World champions South Africa will not only aim to get Peter de Villiers' reign as coach off to a winning start against Grand Slam winners Wales in Bloemfontein on Saturday, but also to retain their position as the No.1 side in the International Rugby Board (IRB) World Rankings.

South Africa's victory over England in the RWC 2007 Final took them to the top last October and they sit 1.22 rating points above New Zealand ahead of the mid-year Tests of 2008, although defeat to a Welsh side ranked five places below them could see that tenure come to an end.

The Springboks have won their last seven encounters with Wales, but were the visitors to record their first win on South African soil then the world champions could see their 90.81 rating points fall by as many as three points depending on the result.

However, even in defeat, South Africa (who will be led by John Smit for a record 50th time) could still retain their top spot if New Zealand suffer a first-ever Test defeat by Ireland in their encounter at the Westpac Stadium in Wellington.

Another victory for the All Blacks against Ireland would not result in any change to rating points for either side, with New Zealand ranked six places and 12.41 points above their visitors ? although were the Irish to spring a surprise in Wellington then there could be several changes in the top eight nations.

Ireland could potentially climb two places to sixth depending on the margin of victory and the outcome in Bloemfontein with Wales and France the sides in danger of slipping places. In defeat New Zealand may also swap places with Argentina, who entertain Scotland in Rosario, to give the Pumas their highest ever position.

A repeat of Argentina's victory over Scotland in the RWC 2007 quarterfinals would not impact on either side's rating points given the seven places and 12.50 rating points which separate the sides before the first of back-to-back Tests on South American soil.

By contrast a first win in Argentina (and only second overall) since 1969 could see Scotland swap places with Fiji and also potentially climb above Ireland, depending on the margin of victory and other results across the southern hemisphere.

The IRB Pacific Nations Cup also kicks off in Lautoka on Saturday, with Fiji entertaining Samoa at Churchill Park in the only opening fixture that could impact the IRB World Rankings, with Tonga and Japan facing representative sides in the New Zealand Maori and Australia A respectively.

Samoa were the leading Pacific nation in the 2007 competition, finishing third behind the Junior All Blacks and Australia A, having edged Fiji 8-3 on home soil in Apia. However Fiji are on a high after reaching the World Cup quarterfinals and have their own sights set on claiming top spot among their Pacific rivals.

Fiji are the higher ranked nation at ninth (three places and 4.27 rating points above Samoa) following their World Cup exploits, and victory in Lautoka is unlikely to do more than improve their rating points slightly, although Samoa could slip one place below Tonga to 13th.

Meanwhile, in the northern hemisphere, the final divisional matches in the European Nations Cup 2008 take place on Saturday with Hungary travelling to Vienna to face Austria, and Norway hosting already crowned Division 3B champions Lithuania in Tonsberg.

Hungary and Lithuania are ranked significantly higher than their hosts at 64th and 48th respectively, but being the away sides a victory could see their positions improve by three or four places depending on the margin of victory with their hosts slipping two or three places.

However, were Austria and Norway (who are ranked 89th and 80th respectively) to cause an upset, then a climb of as many as five to seven places is possible, alongside a slide of up to 10 places for their visitors.