Wales will arrive in Gatland's home town of Hamilton knowing they must shred the history books and record a first World Cup triumph over the South Sea Islanders.
If they fail to deliver, then successive defeats after last weekend's agonising 17-16 loss to world champions South Africa, would leave Wales facing a probable pool stage exit.
The quality of their rugby against South Africa suggests Gatland's men will still be firmly in the quarter-final mix after events have concluded at Waikato Stadium.
But Wales have twice gone into World Cup battle with Samoa as favourites, and come horribly unstuck both times, losing 16-13 in 1991 and 38-31 eight years later.
"We are all very aware that we must go out and match the performance from last weekend," Gatland said, as he prepares to oversee a Wales team unchanged in successive Tests for the first time since 2006.
"We must win on Sunday, that is the bottom line. There are no second chances after Sunday, it's that important to us."
Stephen Jones is the only survivor in Wales' current squad from Samoa's last World Cup victory 12 years ago, although there was also a scare when the sides met two years ago before Gatland saw his players scrape home 17-13 in Cardiff.
Wales skipper Sam Warburton added: "I don't think the players are taking notice of what has happened in the past.
"It's all irrelevant. The squad is a lot different now. They have some big ball-carriers, so we know it is going to be a big physical challenge."
Wales will require repeats of the individual and collective heights attained against South Africa to ensure Samoa are kept at a safe distance.
Centre Jamie Roberts and scrum-half Mike Phillips produced probably their best Test match displays since the 2009 British and Irish Lions tour of South Africa, while new fly-half Rhys Priestland was an assured presence and the back-row of Warburton, Dan Lydiate and Toby Faletau again excelled.
Priestland did miss a late drop-goal chance that might have seen Wales topple the Springboks, yet his overall game meant his retention of the number 10 shirt was never an issue.
"Rhys ran when it was on, he kicked into space well and he gave our centres some early ball and options to attack from," Gatland said.
"Having reviewed the game, we were very comfortable with the way he played.
"He missed a drop-goal, but we also had a (James Hook) penalty chance to win the game. At this level, it's about taking your opportunities.
"What you are looking for in your 10 is for them to be calm, relaxed and not show too much emotion after a disappointment.
"You've got to put the moment behind you, you have got to think about the next phase, the next play.
"You watch quality 10s, and they all make a mistake. Sometimes, they make a mistake like kicking the ball out on the full, and you don't see any reaction, maybe apart from a little smile.
"It happens to players in those pivotal positions. They make mistakes, and it's just how they react to it."
Samoa opened their World Cup campaign with a 49-12 success against Namibia, a game highlighted by their juggernaut Leicester wing Alesana Tuilagi scoring three tries.
"Samoa went at Namibia hard early on and got a bit of a lead. We know what to expect from them - they are going to be very tough and physical, and we've got to match that physicality," Gatland added.
"A lot of the guys know Tuilagi from Leicester and what he does there, so he's not unfamiliar to a lot of players. It is no surprise to us he has made an impact early on in this competition."
In Faletau, though, Wales have potentially one of this World Cup's true stars, and another ball-carrying exhibition similar to the one that had South Africa reeling should see his team thrive.
"Toby is such a naturally good rugby player," Warburton said.
"He reads the game well, he always drops back into the pocket when he needs to and he is sensible when he should offload and when he shouldn't offload.
"For a 20-year-old, he is just unbelievably calm. Nothing seems to faze him, and he's a very popular and relaxed guy in the changing room."
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