Known as "Semi-trailer", the hulking ex-Parramatta flyer has been moved from inside centre to the wing with Fiji coach Simon Raiwalui re-jigging his backline for the match on Sunday (Monday AEST).
Fiji realistically now need a win over the Wallabies to keep alive their hopes of moving beyond the pool stages.
"We couldn't dwell on the last match too long," said Raiwalui.
"We did our review and got out of it what we need to do better against the Wallabies.
"Against Wales we carried very well, we had a lot of possession but we turned over the ball quite a lot, I think 17 times, so we worked on that, securing the ball and taking our chances where we have them."
Skipper Waisea Nayacalevu was clear about the importance of the match.
"It's a do or die game this week for us, so that's our mentality," he said.
"We take Australia seriously and we've prepared well this week."
In a dramatic opening Cup clash against Wales, Radradra fumbled a last-ditch pass with the tryline beckoning that could have turned the result.
But the 31-year-old still earned his keep, beating the most defenders, six, from the third-most carries among his team, tallying 16.
Playing for the Eels in the NRL between 2013 and 2017, Radradra had a stunning strike-rate with 82 tries from 94 games.
Fiji, who haven't beaten Australia since 1954, may see some vulnerabilities in the Wallabies defence that were exposed by Georgia, with the likes of winger Mark Nawaqanitawase and fullback Ben Donaldson not noted for their tackling.
Josua Tuisova will wear Radradra's No.12 jersey in the Stade Geoffroy-Guichard match while in other changes to the backs, Jiuta Wainiqolo comes in on the right wing for youngster Selestino Ravutaumada and Simione Kuruvoli replaces halfback Frank Lomani.
Levani Botia is the new openside flanker with Lekima Tagitagivalu, another of Fiji's try scorers against Wales, switching to blindside.
Utility back and Sevens Olympic champion Vilimoni Botitu, a squad injury replacement for five-eighth Caleb Muntz, will start on the bench.
Fiji: Ilaisa Droasese, Jiuta Wainiqolo, Waisea Nayacalevu, Josua Tuisova, Semi Radradra, Teti Tela, Simione Kuruvoli, Viliame Mata, Levani Botia, Lekima Tagitagivalu, Te Ahiwaru Cirikidaveta, Isoa Nasilasila, Luke Tagi, Sam Matavesi, Eroni Mawi.
Replacements: Tevita Ikanivere, Peni Ravai, Mesaki Doge, Temo Mayanavanua, Albert Tuisue, Frank Lomani, Vilimoni Botitu, Vinaya Habosi.
