Victory would give the Scots second place behind South Africa in Pool B and send them through to a last-eight game against Australia or Wales.
Defeat would allow Japan, conquerors of the Springboks, to grab that berth if they can beat the United States on Sunday or score four tries and draw.
It would mean a second successive World Cup failure for Scotland, after dropping out at the pool stages in 2011.
"For a lot of us this is going to be the biggest match of our careers," Scotland number eight David Denton said this week.
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"For most of the people on our team this is our first World Cup, but now we’ve essentially got a playoff game."
Samoa have suffered a poor campaign with just one win, over the U.S., and cannot advance to the quarters. But they may be all the more dangerous as they set out to salvage some national pride.
"At the moment we have a country that is feeling a bit sad. Not just that, we’ve got a lot of talent but we haven’t shown it. We haven’t shown anything of it all the tournament," coach Stephen Betham said.
"We haven’t played well all World Cup but maybe we’ve got one in us."
Newcastle is the northernmost of the 13 tournament venues, making it the next best thing to a home game for the Scots, whose supporters -- some in kilts -- will vastly outnumber those cheering for Samoa.
On a sunny and still autumn day, conditions are perfect at St James' Park after overnight repairs to the turf that was heavily churned up in places from the New Zealand-Tonga game on Friday night, won 47-9 by the All Blacks.
First-choice flyhalf Finn Russell returns for Scotland after missing the defeat by South Africa. Coach Vern Cotter has also recalled centre Mark Bennett in a near full-strength team.
Betham has made seven changes for the Pacific Islanders, fielding new combinations in midfield and among his loose forwards after losing to Japan in their previous game.
Rey Lee-Lo and George Pisi will form a new centre pairing, while Maurie Faasavalu, Jack Lam and Alafoti Faosiliva will be together in the back row for the first time.
(Editing by Ed Osmond)
