Auckland - Samoa must upset defending champions South Africa on Friday or hope Fiji conquer Wales to reach their first Rugby World Cup quarter-final in 16 years.
The Samoans haven't got close to the Springboks in three previous World Cup encounters and face their tournament moment of truth just five days after their physically demanding 27-7 win over Fiji at Eden Park.
Samoa may still squeeze into the last eight with a bonus point loss coupled with a Fijian upset of Wales in Hamilton on Sunday.
The Springboks are unbeaten in the tournament and appear to be running into form ahead of the quarter-finals where they are likely to face fellow two-time champions Australia in Wellington.
South Africa have named their strongest available team, with returning lineout general Victor Matfield back from two games out with a hamstring injury replacing rested John Smit as captain in one of seven changes from their last start, an 87-0 drubbing of Namibia.
With Smit standing down after playing in the first three games, Bismarck du Plessis finally gets his chance at hooker after cooling his heels on the replacements bench.
"If you play any of the Pacific island teams I think the set pieces are very important. If you give them too much ball they're very dangerous so that's one thing we're focusing on," Matfield said.
"They're a brute side so it won't be easy but we're working hard to hopefully put them under pressure in the lineouts and in the scrums."
Matfield, who will lead the Springboks for the 17th time, is lining up for his 109th Test match to join Smit as the most capped Springbok.
"It's the first time since our first game we have the privilege to select the team from 29 fit players," said Springbok coach Peter De Villiers
Only lock Bakkies Botha, who continues to struggle with an Achilles heel injury, was unavailable for selection.
De Villiers believes Samoa's departure from their traditional free-flowing rugby for a more structured game will make them difficult.
"It will make them more difficult to play because of the structure. They'll keep the ball for longer periods," he said.
"They will be very strong at the breakdown like they normally are. Because they went into structure they forfeit something, but they gain a lot of other things."
Discipline under pressure will be Samoa's biggest concern as they were guilty of throwing away their chances in a crucial 17-10 loss to Wales by conceding penalties at the breakdown.
It will be South Africa's composure under fire that will make them hard to tackle at North Harbour, where they will draw a big following of expats living on Auckland's north shore.
Samoa lost 42-12 to South Africa in their only World Cup quarter-final appearance in the republic in 1995 and have also lost pool games 60-10 (2003) and 59-7 (2007).
"I think it is all about attitude. You can't go into the World Cup half-hearted. You can't have the attitude that you are going to come second," Samoa skipper Mahonri Schwalger said.
Schwalger said his team was looking forward to the opportunity of testing themselves against the defending champions.
"You have to make sure you are on the top of your game if you want to compete against these guys. South Africa is the world champ and it won't be an easy game," he said.
"We will focus on what we need to do on the field. These are the games you want to play rugby for. You do not take these opportunities lightly."
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