Fiji needs only one point from the match on Sunday to reach the quarterfinals for the first time since 2007. If Fiji get nothing, Australia will qualify as the Pool C runner-up to Wales.
Usually a centre, Botitu's only previous flyhalf start for Fiji was against Scotland last November at Murrayfield. He's started once in the 10 jersey for his Castres club in three years, last May.
Caleb Muntz was Fiji's 10 until he suffered a tournament-ending knee injury days before the tournament. Teti Tela has started all three previous pool games; wins against Australia and Georgia and the opening loss to Wales.
Botitu will be served by goalkicking scrumhalf Frank Lomani, who has come off the bench in the last two games and added 10 vital points.
Among the six changes after beating Georgia 17-12 last weekend in Bordeaux, Northampton-bound Temo Mayanavanua has gone into the second row and the Drua's Meli Derenalagi into the back row. Derenalagi will make his tournament debut.
Vinaya Habosi replaced Semi Radradra on the left wing, and Sireli Maqala displaced Ilaisa Droasese at fullback.
Portugal has dropped captain Tomas Appleton to the reserves and handed the inside center position and captaincy to Jose Lima.
The four other changes following the 34-14 loss to Australia in Saint-Etienne last Sunday include Francisco Fernandes at loosehead prop after 26 minutes off the bench last weekend, and Steevy Cerqueira into the second row.
Rafael Simoes has replaced Thibault de Freitas at No. 8 in the third change to the pack.
Manuel Cardoso Pinto starts at fullback for the first time since February 2022 after 24 minutes off the bench in the Rugby World Cup.
Portugal drew with Georgia 18-18 two weeks ago but is still waiting for its first win at a Rugby World Cup.
Fiji:
Sireli Maqala, Selesitino Ravutaumada, Waisea Nayacalevu (captain), Josua Tuisova, Vinaya Habosi, Vilimoni Botitu, Frank Lomani; Viliame Mata, Levani Botia, Meli Derenalagi, Temo Mayanavanua, Isoa Nasilasila, Luke Tagi, Sam Matavesi, Eroni Mawi. Reserves: Tevita Ikanivere, Peni Ravai, Mesake Doge, Te Ahiwaru Cirikidaveta, Albert Tuisue, Peni Matawalu, Teti Tela, Iosefo Masi.
Portugal:
Manuel Cardoso Pinto, Raffaele Storti, Pedro Bettencourt, Jose Lima (captain), Rodrigo Marta, Jerónimo Portela, Samuel Marques; Rafael Simoes, Nicolas Martins, David Wallis, Steevy Cerqueira, José Madeira, Diogo Hasse Ferreira, Mike Tadjer, Francisco Fernandes. Reserves: David Costa, Duarte Diniz, Anthony Alves, Duarte Torgal, Joao Granate, Joao Belo, Tomas Appleton, Vincent Pinto.
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