At the age of 42, the legendary New Zealand centre was signed by the French giants last month as a medical joker for the injured Charles Ollivon.
Nonu was signed as cover and there was doubt as to whether he would be taking to the field, but on Saturday, he could become the oldest player to feature in the Top 14.
According to Midi Olympique, the All Blacks great, whose international career ended almost a decade ago, will be named on the bench for Toulon's league match against Castres.
"Above all, I respect the man and the player he is. But, as a coach, I judge what is good for my team at that moment," head honcho Pierre Mignoni said.
"At the end of the first week, seeing our injured players, I asked him: 'Wouldn't you like it?' He looked at me and didn't say no. We tested him a lot before making a decision."
Nonu is 43 in May but this is not a vanity project for either party, while the ex-All Black's inclusion in the Toulon squad has been accepted by the players.
Signing a 42-year-old would have probably raised a few eyebrows, but France international Esteban Abadie reckons that he has already added plenty of value and also compared him to another New Zealand great.
"What strikes me about him is his humility. I experienced that with [Joe] Rokocoko at Racing. They are legends, and yet, they arrive with the motivation and humility of a youngster," Abadie said.
Nonu has been training over the past few weeks after signing for Toulon in late-February and lock Matthias Halagahu believes that Mignoni and Nonu have been preparing for this moment.
"We felt it coming little by little. Pierre took the time to talk to the centres, and that was important. If the leaders had said no, I don't think he would have taken the risk," Halagahu said.
"But he will bring us 10 per cent more in terms of demands and consistency. He's here every morning at 7am. He works harder than everyone else.
"He's not here to take someone's place, nor to be a starter in every game, he's here to lend a hand."
Nonu effectively stayed in New Zealand until his early 30s - the only stint abroad being a short-term sabbatical in Japan - and realised his All Blacks dream by earning over a century of caps and winning the World Cup twice.
Following the global tournament in 2015, the centre moved overseas and spent several seasons at Toulon before signing for San Diego Legion in Major League Rugby.
He has remained with the American side, playing a key role despite entering his 40s, but Nonu is now back in France and could make Top 14 history on Saturday.