When Wales lost to Western Samoa in 1991 in Cardiff and became the first foundation union to fail to qualify for a World Cup quarter-final, the joke was that it had been just as well they were not playing the whole of Samoa.

Western may have long gone but Wales face a shoot-out against Samoa in Hamilton on Sunday. Defeat would almost certainly see them perish at the group stage for the fourth World Cup in six, although a group that also includes South Africa and Fiji may see the team that finishes second suffer two reverses.

Wales's narrow defeat by the holders South Africa in Wellington last Sunday, when they missed two late kicks that would have won the match, was the one rousing performance by a Six Nations country in the opening round and it should have yielded more than a mere bonus point.

While the All Blacks are widely criticised for their policy of rotating selection, the New Zealand-born Wales coach, Warren Gatland, named an unchanged starting line-up with the only new face on the bench being the prop Gethin Jenkins, who has recovered from a calf injury.

It is five years since a Wales coach last said "same again". They now face a shoot-out against Samoa in Hamilton on Sunday. Defeat now would almost certainly see Wales perish at the group stage for the fourth World Cup in six, although a group that also includes South Africa and Fiji may see the team that finishes second suffer two reverses.

Wales have had a week to recover from their opening match, but Samoa have just a four-day turnaround for a game that is highly significant to both sides. Wales have a poor record against Samoa and Fiji in World Cups, losing to the former in 1991 and 1999 and the latter four years ago.

"There are no second chances for us," Gatland says, who is returning to his home town. "We are all aware that the bottom line is that it is a game that we must win. It is that important to us. We must match the performance of last Sunday and that is why we have named the same side. We know what to expect from Samoa and we have to match their physicality."

Despite the defeat, last Sunday was probably Wales's best performance since they won the 2008 grand slam under Gatland. Had they not been hit by injuries to five senior players, they would have been able to match the Springboks' resources on the bench that ultimately proved the difference between the sides.

Wales surprised the Springboks with their sustained ferocity. Three players who had made an impact with the Lions in South Africa in 2009, Jamie Roberts, Mike Phillips and Alun Wyn Jones, rediscovered their form of that tour, showing a hardened resolve that proved infectious.

Wales were happy to seek contact, Roberts rarely taking the ball at pace through the channel of the outside-half Morne Steyn, a player not known to relish defending, but they will need to create space against a side who relish head-on confrontation but also play in the right areas. Wales have in the past been vulnerable against Samoa and Fiji because they have traded control for anarchy.

"We have to make sure our patterns are correct," Shane Williams, the Wales wing, said. "This week is going to be even more important than the last one. This is a different Samoa team to the ones we have faced in the past. There is more structure to their game and their set pieces are good, but as soon as you start playing sevens against them you are in trouble."

Gatland has not been afraid to invest in youth. The average age of Wales's back row is less than 23 and Sam Warburton, Toby Faletau and Dan Lydiate have just 37 caps between them, but they eclipsed the vastly more experienced South African loose trio last Sunday and their ability to force turnovers may be decisive against Samoa.

Wales are not known for their tendency to back up performances. If the defeat to South Africa highlighted an inability to defeat the highest-ranked sides that has irked Gatland during his four-year reign, what has also maddened him is inconsistency.

If Wales show the same drive and determination that left South Africa hanging on at times, they will surely win but it is far from a given. What should galvanise them is the knowledge that defeat would surely mean an early ticket home, and while that has not been the case in the past, Wales have become mentally tougher under Gatland. Sunday will show by how much.