Ireland centre Gordon D'Arcy believes there will be no margin for error when he locks horns with rising Wales star James Hook in Sunday's Six Nations opener.

Hook made his Test debut on the summer tour to Argentina and heralded his arrival as a world-class talent when he stepped off the bench to rescue a seemingly lost cause in the 29-29 draw with Australia in November.

The gifted 21-year-old, who has the running skills to match his outstanding kicking game, has already been compared with Wales legend Barry John despite winning only six caps.

He faces his toughest test yet when he collides with Ireland's vaunted midfield at the Millennium Stadium and opposite number D'Arcy is relishing the prospect of their duel.

"I'm not about to give James any advice because I don't want him to get any better," he said. "But the graph goes very quickly up and you have to keep working because, when you reach international level, it's the little things that make a big difference - making the right pass at the right time, making the right kick at the right time.

"I'm really looking forward to playing him. He'll be a very, very tough opponent. I like guys I have to sit there and worry about.

"He is very confident in his skills and he is a very attacking, talented player. I really look forward to playing against him.

"The two things that stand out for me are the try he orchestrated for the Ospreys against Sale in the Heineken Cup.

"Time was up and they just kept the ball going and he was integral. He must have taken the ball seven or eight times for that try, which Shane Williams scored and they won the game.

"The other occasion was when we played the Ospreys, he came on with 15 minutes to go and they picked up their tempo.

"He is a hard guy to get hold of. His ability to step in a close area, send you one way and go, means it is very, very hard to get a clean hit on him."

D'Arcy has also experienced the highs of enjoying success early in his Test career.

After five substitute appearances stretched over four years, the Leinster centre finally won a start in the 2004 Six Nations and went on to produce a string of sensational performances that saw him named player of the tournament.

Injury and a loss of form - most noticeably on the Lions tour to New Zealand a year later - followed but, last autumn, the 26-year-old was back to his dazzling best with eye-catching displays against South Africa and Australia.

"Of course I worried that I wouldn't get back to where I was in 2004, I wouldn't be human if I didn't," he said.

"I've been down and got back up plenty of other times. When you are injured or not playing well, it is very hard to believe you will get back.

"The Lions tour didn't go well and I had a shoulder operation and I was down in the dumps after that tour. The operation was a great opportunity for me to reassess where I want to go.

"I am a different player now to 2004. I was an out-and-out 13 then. As Brian O'Driscoll has described it, outside centre is like a centre forward, 12 is not so much of a striker. There is a little bit more graft to it.

"I have had to change positions and learned a huge amount off Ronan and their ability to control the game. I am a different player but there is still loads of bits of my game that I am not happy with and that I will be working hard on."