Nayacavou, who featured for Scotland in the first round of the series in Gold Coast, will replace injured forward Chris Dean.
The former Lelean Memorial School student is expected to play against the Digicel Fiji 7s side in pool play.
Fiji will play Australia in its first pool match of the South Africa 7s at 11.28pm Saturday, France at 2.34am Sunday before facing Scotland at 6.14am Sunday.
The Digicel Fiji 7s team is expected to meet either England, Samoa or Argentina in the Cup quarterfinals and barring any upsets, they will face either New Zealand, Kenya, South Africa or Wales in the semis.
The Cup quarterfinals will start at 11:39pm Sunday, the Cup semis at 3:49am Sunday and the main final will be at 6:30am Monday.
Story by: Akuila Cama
