AFTER four years of pledges to ‘learn the lessons’ from painful defeats the time for discovery is over. At 6pm there will be no next time for one nation.

The World Cup building phase is long gone, it’s win or bust in Wales’ quarter-final against South Africa at Twickenham this afternoon.

One team will return next weekend to the famous ground, which has been absolutely jumping this tournament, while the other will have checked out of their hotel and be back on club duty.

There is no margin for error. Mess up today and there can be no positives.

Wales have been at it again this week, saying that they have learnt the harsh lessons from their failure to make a two-man advantage count against Australia.

Apparently you need to take your chances and be cutthroat at Test level. Who’d have thunk?

Failure to grasp those opportunities will no longer have the consolation of being an experience that will serve them well come the World Cup. Japan 2019 is a long way off.

But Wales are confident that they can strike a first blow for the northern hemisphere.

Power is vital in Test rugby but it’s even more important against the Boks, who have gone back to basics following their poor Rugby Championship and shock loss to Japan.

They will be direct with their imposing pack, cunning through master tactician Fourie du Preez and, if needed, ruthless out wide through Bryan Habana and JP Pietersen.

There was some relief in South Africa that veteran lock Victor Matfield suffered a tight hamstring; while he would have brought experience there is the feeling that Eben Etzebeth and de Jager provide more energy and oomph.

But Wales have proved they can match the best sides in the world in the collisions with Dan Lydiate, who is back from injury, Luke Charteris and Jamie Roberts set to play key roles.

At the contact area they can thrive with Sam Warburton and Gethin Jenkins while in attack they will be direct with George North having to look for work from his left wing.

And then there’s an added strand to it all for us in the east, we will be watching closely at outside centre with our fingers crossed that Tyler Morgan does a solid job.

Anyone who has watched Newport RFC and the Dragons knows that he is an exciting talent with pace on the outside break, power and an offloading game but this afternoon he just has to repeat what he did against Fiji – do the basics well.

Wales should have beaten the Aussies to be up against Scotland tomorrow but it’s not mission impossible against the Boks, who they know that they can beat the Boks thanks to last autumn’s 12-6 success in Cardiff, admittedly against a weakened visiting side.

The defence snarled on that afternoon and it will today – this is not going to be a thrill a minute, free-flowing affair.

Wales’ penalty and error counts must be low and they must not allow South Africa to build a lead because they are a nightmare to chase and have quality sat on their bench.

Dan Biggar has the edge on South African counterpart Handre Pollard as a kicker but his only miss of the tournament, a relatively simple effort against Australia on the stroke of half-time, proved to be hugely costly.

Wales need to be perfect today if they are to be watching events from Cardiff this evening to see who they will face in the semi-finals.

They’ve won a tight one at Twickers and lost one. It’s another tough one to call and this time there is no safety net – profligacy equals Guinness Pro12, Aviva Premiership and Top 14 duties before November.

Wales: G Anscombe, A Cuthbert, T Morgan, J Roberts, G North, D Biggar, G Davies, G Jenkins, S Baldwin, S Lee, L Charteris, A W Jones, D Lydiate, S Warburton (captain), T Faletau. Replacements: K Owens, P James, T Francis, B Davies, J Tipuric, L Williams, R Priestland, J Hook.

South Africa: W le Roux, JP Pietersen, J Kriel, D De Allende, B Habana, H Pollard, F du Preez (captain), T Mtawarira, B du Plessis, F Malherbe, E Etzebeth, L de Jager, F Louw, S Burger, D Vermeulen. Replacements: A Strauss, T Nyakane, J du Plessis, P du Toit, W Alberts, R Pienaar, P Lambie, J Serfontein

Referee: Wayne Barnes (England)