Director of rugby Wayne Smith said Tui had shown all the tendencies to play fullback.
"We are giving everyone opportunities. We've got a strong squad, including our outside backs. It's all about combinations and we don't know what is down the track.
"Ruby works hard, covers a lot of ground, gives us cover if it is needed, and another option."
Tui said it was exciting to play fullback, and the move reflected how Smith always thought about their play.
"We have grown so much as a team in the last 12 months. My eyes are lighting up at the opportunity.
"The cool thing is I have the experienced Renee [Wickliffe] on the right [wing] and another good friend of mine [Portia Woodman] on the other wing, so we have solid connections on the field.
"Fullback is all about reading the game, and I feel we have six eyes looking after that.
"It's always an honour to wear the jersey, and I would play prop if I had to."
Smith said Wales was not a side unknown to them.
"We have watched every game of every team who are here over the last two years, so we are well versed on the likes of Wales and Scotland. We have done the homework on those previous games and the ones last weekend.
"As to the northern teams and the way they play…rugby is rugby, and you can play it many ways. I don't think there is a northern way and a southern way."
Tui said the players knew that rugby in Wales enjoyed similar popularity in New Zealand.
"We have that in common, and I will respect the red jersey when we play them.
"[Jasmin] Joyce is a speedster, keeps the ball alive, drives forward, picks and goes often, and can chase down and tackle. She has a lot of toe, as do some of our team, so it will be interesting this weekend. Stay tuned."
Smith said there was still work to do in managing how the players performed in front of bigger crowds, and they would take a similar approach to that they used against Australia when they play Wales.
"The players are still learning that. We were not at our best [at Eden Park] but then scored 41 points in 45 minutes, which shows we have the ability to switch on when we are ready.
"All of the matches are big occasions in the tournament, including Wales at Waitakere. And we want to be back at Eden Park, so the next game is part of that process, getting more experience using the leadership we have in the team to help achieve that goal," he said.