Naholo said he was at home with his brother when he got the call from All Blacks manager Darren Shand, and he assumed it was bad news.
"It's a humbling experience to be here and part of this tonight," he said.
The Fijian-born player decided to travel to his homeland to seek traditional medicine which consisted of massage and herbal remedies.
Hansen, who declared himself a "believer", said the All Blacks medical staff kept an open mind about the treatment.
"Our medical staff are very open-minded people as we all should be," he said.
He added that Naholo's recovery was about 10 days ahead of schedule and that his selection was about risk and reward and the latter was much bigger than the former.
"We've been in this situation before," Hansen said. "Kieran Read went into the last world Cup injured and we had to wait until the quarter-finals for him. What are the rewards of taking Waisake? He's a try-scoring machine, he's X-factor, he brings something to the team which others in the group don't bring.
"We can't win this World Cup by just having ordinary, we've got to have something different and he provides that."
McCaw added: "It's just awesome that he got himself right and gave himself the opportunity."
While the selection of Naholo and other players considered to be on the fringe such as Colin Slade and Nehe Milner-Skudder were the positive stories, Hansen and skipper Richie McCaw was mindful of the 10 players who will be left behind, most notably Israel Dagg, Cory Jane and Lima Sopoaga.
"You feel for them absolutely... I think there's been a bit of anxiety across everyone because you certainly weren't assured of anything," said McCaw. "Unfortunately that's the nature of what we do. You can't pick everyone.
"We're just so lucky in New Zealand we have men of that calibre that unfortunately we can't take but if we get injuries they're pretty good guys to get on the plane and get over there. It would be pretty horrible to hear that today, they will be disappointed.
McCaw added of the All Blacks' chances: "There are 20 teams on the start line who think they can do the job and we're just one of them. But I think this crew is different to the one in 2011 you have to remember that and the team who gets the job done is the one who get it right in the next six weeks, regardless of what happened last week, last year or four years ago. That's just reality and the quicker you get your head around that the better."