This could just be the biggest game of Round One in the toughest pool at the 2011 World Cup, a hard one to call.

Ancient history suggests a South African win, but Wales's recent performances suggest that such could be unlikely. It is an important match as it determines much of the teams' paths though in neither case is defeat exclusive, as England showed in 2007.

But it will take a lot of character to get the path straight again.

A close match can turn on seemingly small things in this game of consequences - an error here and a decision there, a bit of brilliance and missed tackle, a Shane Williams moment, a Morné Steyn drop. There may also be victory and defeat in fitness and in the physical battle. The bench may count heavily.

Wales have been involved in strong contests lately while South Africans have been husbanding their strength, putting out a full side only twice during the Tri-Nations.

Schalk Burger has had  a long lay-off and Frans Steyn looked decidedly out of condition when he did play for a while against the Wallabies. Fourie du Preez has had a long lay-off, too, and was not looking sharp at all in his comeback, not the dominant force of yore.

A lot will depend on up front grunt as is usually the case in close affairs, and the big Springboks, even without enforcer Bakkies Botha, would expect to dominate there and then be able to bring effective muscle from the bench, especially Bismarck du Plessis and Willem Alberts.

Wider out Wales have, in recent times and possibly always - been able to achieve more with less by being so cleverly evasive.

They still have Shane Williams, James Hook and Jamie Roberts to do that sort of thing. But then South Africa has smooth Jaque Fourie and cunning poachers in Bryan Habana and Jean de Villiers.  A missed tackle could be expensive.

It has the makings of an exciting, unpredictable match.

Players to watch:

For Wales: Shane Williams, always, the bright spark of the rugby field, and big George North on the other side with clever, surprising James Hook between them.

For South Africa: Jaque Fourie and Fourie du Preez are the men who can make most difference. And Bryan Habana - so near to the astonishing form of 2007 but not as effectively there yet. The battle of the tackle could be decisive and here there will be especial interest in squat, strong Heinrich Brüssow - and how Mr Barnes views his activities.

Head to Head: Front rows. Wales have an excellent front row, South Africa a competent one. South Africa's may just have the better back-up. But the clash here could just be critical, not only from a morale point of view but also what it can do for loose forwards. Jamie Roberts vs Jean de Villiers - strong, clever, experienced centres. Goal-kicking always counts - the Steyns against Hook and Priestland. The Steyns look to have the edge. But then they look to have the edge on must players who aim kicks at goal.

Recent results:
2010: South Africa won 29-25, Cardiff
2010: South Africa won 34-31, Cardiff
2008: South Africa won 20-15, Cardiff
2008: South Africa won 37-21, Pretoria
2008: South Africa won 43-17, Bloemfontein
2007: South Africa won 34-12, Cardiff
2005: South Africa won 33-16, Cardiff
2004: South Africa won 38-36, Cardiff
2004: South Africa won 53-18, Pretoria
2002: South Africa won 19-8, Cape Town

Prediction: South Africa by five points more or less.

Teams:

South Africa: 15 Frans Steyn, 14 JP Pietersen, 13 Jaque Fourie, 12 Jean de Villiers, 11 Bryan Habana, 10 Morné Steyn, 9 Fourie du Preez, 8 Pierre Spies, 7 Schalk Burger, 6 Heinrich Brüssow, 5 Victor Matfield, 4 Danie Rossouw, 3 Jannie du Plessis, 2 John Smit (captain), 1 Tendai Mtawarira.
Replacements: 16 Bismarck du Plessis, 17 Gurthrö Steenkamp, 18 CJ van der Linde, 19 Johann Muller, 20 Willem Alberts, 21 François Hougaard, 22 Butch James.

Wales: 15 James Hook, 14 George North, 13 Jonathan Davies, 12 Jamie Roberts, 11 Shane Williams, 10 Rhys Priestland, 9 Mike Phillips, 8 Toby Faletau, 7 Sam Warburton (captain), 6 Dan Lydiate, 5 Luke Charteris, 4 Alun Wyn Jones, 3 Adam Jones, 2 Huw Bennett, 1 Paul James.
Replacements: 16 Lloyd Burns, 17 Ryan Bevington, 18 Bradley Davies, 19 Andy Powell, 20 Tavis Knoyle, 21 Scott Williams, 22 Leigh Halfpenny.

Date: Sunday, 11 September 2011
Venue: Regional Stadium, Wellington
Kick-off: 20.30 (08.30 GMT)
Expected weather: There is a 40 percent chance of rain with a high of 16°C, dropping to 7°C
Referee: Wayne Barnes (England)
Assistant referees: George Clancy (Ireland)), Vinny Munro (New Zealand)
TMO: Matt Goddard (Australia)

By Paul Dobson