Samoa and Tonga will meet in a sold-out Parramatta clash on Sunday night, with the winner avoiding Australia in the World Cup semi-finals.
Both sides have already qualified; the result will determine their semi-final opponents and positions.
Sua Fa'alogo moved to the wing after Deine Mariner injured a hamstring in Samoa's opening game against France.
The 23-year-old scored four tries against France and two against Papua New Guinea, while recording nine line breaks and four try assists across the matches.
Though named Melbourne Storm's player of the year as a fullback, Fa'alogo has played on the wing before.
Samoa coach Ben Gardiner said, "I've been really impressed and we had great belief and confidence in the fact that he could shine."
Gardiner said Fa'alogo was born in Samoa and brought knowledge of the nation's traditions, culture and heritage to camp.
Lock Francis Manuleleua, 22, has been man of the match in both games after a rookie season in Newcastle's second row.
Gardiner praised Manuleleua's game knowledge and energy, saying, "He is a great team player and brings huge energy."
Gardiner expects strong support for Samoa from communities in Samoa, America, Australia and New Zealand, while describing Samoan and Tongan fans as deeply passionate.