John O'Sullivan talks to the New Zealand native who fills the scrumhalf berth against Australia

Isaac Boss doesn't shirk a challenge, conditioned by his formative years in rugby to scrap for the number nine jersey. A member of the victorious New Zealand 1999 Under-19 World Cup team, he played the entire Super 12 season with the Waikato Chiefs as first-choice scrumhalf.

The arrival of All Black Byron Kelleher initially saw him switch to fullback and then move to the Wellington Hurricanes where he vied with current New Zealand squad member Piri Weepu for the starting halfback role.

On Sunday he gets his first opportunity to start for Ireland having won three caps previously during the summer tour to the Southern Hemisphere.

He's replacing one of Irish rugby's icons in the 70-times capped Peter Stringer. He knows the jersey's on a term loan but, like every professional sportsperson in a similar position, Boss is hoping his performance will blur the selection lines a little.

Ireland coach Eddie O'Sullivan wants to see how the 26-year-old Boss handles the pressure of beginning a Test match and not just offering some late cameos in matches, already largely decided. The New Zealander born in Tokorua, Waikato, who qualifies for Ireland through a maternal grandmother from Glenarm in Antrim, knows he's made the right decision to travel to Ireland.

He's always been aware of his family's Irish background and when Ulster sought his signature last year he didn't hesitate. It took him a while to settle last season but he's now Ulster coach Mark McCall's first-choice scrumhalf.

The first thing he did on learning of his elevation to a starting role was bounce a few texts to New Zealand. After training he called his parents, who didn't object to the fact they'd only been in bed a couple of hours when they learnt the context of the call. He smiled: "They (my family) get up and watch every Irish game as I used to do when I was young.

"There is probably a little bit more reason to get up at 5am on a Monday morning. If I make a mistake my brothers will be the first to let me know.

"My experiences in New Zealand in coming through (representative) rugby meant that I didn't have a lot of opportunities to start (in the last few years).

"There's a lot more at stake on Sunday collectively and individually but (in some respects) things don't change. You have different calls and different moves but in terms of starting a match it's about handling the build-up. I'm determined to enjoy the experience and my attitude will be to get out there and play and hopefully things will bounce the right way."

He is aware he'll bring a different dynamic to the scrumhalf role but paid tribute to the man he succeeds. "We are very different but it's up to me to slot in. He's got a great partnership with Rog (Ronan O'Gara) and it's important that I fit in and the team doesn't lose anything. I bring different aspects to the game in and around the rucks and mauls. I have to get in there and fulfil my responsibilities as a scrumhalf first.

"You don't get too many chances with Strings (Peter Stringer) around and he's been consistent for the last 70 odd games. He's been playing so well and it's up to me to take my opportunity. I don't look beyond this game," he added.

"I'm looking to try and put on as much pressure as I can. While I have been on the bench, I have been able to pick up a few things in terms of the way he does things within the team. I can certainly learn from him. Everyone's goal is to get a starting place. I have three caps with a total of about 25 minutes so hopefully I'll double or triple that this week. I'm enjoying being part of the Irish set-up."

Opportunity knocks on Sunday.