Meet the Australian Wallabies' "bula boys": two softly-spoken, guitar playing, Fijian powerhouse back line stars ready to grab Australian rugby and take it to World Cup glory.

That's the plan for Kuridrani and Speight as they prepare to play their first Test together for their adopted country.

Speight will make his Test debut against Ireland, joining Kuridrani who has cemented his place in the starting side, and their Fijian communication will bamboozle teammates and opponents.

"I'm really happy for Henry, I can't wait for his chance," Kuridrani said. "He's come a long way, everyone is waiting for him to pull on that gold jersey. His family and people back in Fiji will be waiting for it.

"We talk in Fijian all the time, on the field and off the field. We tell jokes from Fiji and that's pretty good for me."

Kuridrani has been the Wallabies' best player for the past year and has cemented his place as the first-choice outside centre.

He has missed just three Tests since making his debut last year, and two of those were only because he was suspended.

The 102 kilogram, 196 centimetre midfield cannonball credits a childhood of watching Stirling Mortlock and Ireland's Brian O'Driscoll tear up opposition teams for his desire to win the Wallabies No.13 jersey.

"He's been unbelievable, everyone talks about Israel [Folau] and rightly so, but Tevita is basically the same size," said teammate Will Genia.

"For someone that big to be able move the way he does … it's pretty amazing. He's a physical guy, runs hard and has been the best player for the Wallabies this year.

"But the other thing he brings is his personality, he lightens the mood every time at training because he doesn't take things too seriously. That's a really good influence on the group."

Kuridrani and Speight's journeys into the Wallabies are miles apart, but the ACT Brumbies teammates are almost inseparable on and off the field.

In fact, they've been known to swap rooms with teammates on tour because they feel comfortable when the other's around.

They bought ukuleles and guitars in Cardiff in the second week of the Wallabies tour and have been entertaining the team with their musical ability as well as their Fiji power.

"The Fijian connection … just listening to them talk, it sounds like they're mumbling and then one will laugh and they'll just walk off," Genia said.

Kuridrani, 23, is the hard-running Wallabies outside centre known as the "K-Train", who is looming as a key to Australia's hopes of World Cup success next year.

He grew up in the same village as Canberra Raiders try-scoring great Noa Nadruku and is the cousin of dual international Lote Tuqiri and Canterbury Crusaders giant Namani Nadolo.

Speight is the flying winger who will make his Test debut against Ireland after a four-year eligibility wait to play for Australia.

He grew up with his grandfather, former Fiji president Josefa Iloilo, and his uncle is Fijian coup leader George Speight.

"We both grew up on the Fiji main island, he's from the eastern side and I'm from the western side," Kuridrani said of Speight.

"We didn't know each other before we met up in Canberra at the Brumbies. We brought some kava over here with us, but we haven't had it yet. Maybe after the weekend, maybe at the end of the tour."

Kuridrani's first trip to Ireland last year left a sour taste in his mouth after he was suspended for five weeks for a tip-tackle.

"It was very disappointing last year, it was the last five minutes of the game when I did it so it was pretty silly for me," Kuridrani said.

"But I'm just here to do a job, I feel I've stepped up and the last two games of the tour are really important for us as a team moving forward."

The ARU opened contract talks with Kuridrani last month to try to keep the rising star away from the clutches of rich European clubs.

But after admitting he was shy and nervous when thrust into Test duties last year, Kuridrani says his only focus is on-field success and a World Cup goal.

"The World Cup is one of my goals and it's a big one for me … hopefully I can just continue my performance and make it," Kuridrani said.

"Last year was a learning stage for me, but right now I'm pretty confident just knowing what my role is and what the team needs from me.

"I feel really different this year with confidence on the field. I was a bit nervous getting the calls out last year and not sure of what I had to do.

"My physicality has changed compared to last year. For me it's about getting over the gain line and strong carries."