Sonny Bill Williams is adamant he is ready to start in the inside centre berth and is relishing the chance to prove his ability to the All Blacks' selectors.

Having been out of the picture for New Zealand's final Tri-Nations game against Australia, Williams looked destined for few chances in the World Cup. That all turned on Wednesday, though, when the 26-year-old was the surprise inclusion at inside centre for the All Blacks' opening World Cup game against Tonga on Friday.

And the former rugby league man is adamant he has not struggled as a spectator and is excited to start the tournament. "I want to take it in two arms and really give it a good crack. That's what I am aiming to do and am really excited to be playing," he said. "We want to start off with a good bang and I am thankful I am part of it."

After delays in confirming his future commitments, Williams, who has been linked with a return to league as well as continuing his boxing career, said everything else was irrelevant and that he was concentrating on playing Tonga. And coach Graham Henry revealed his advice to Williams would be not to try and do it all in five minutes, that the game lasted for 80.

"I thought he played very well in South Africa but I do think when the players do get a chance, and haven't played for a while they try and push it too much, probably overdo it and I guess patience is going to be key," Henry said. "And if he just lets his natural ability control the way he plays, he will play well."

Williams is looking to fit into the team role adding: "I guess it is toning it down a bit, sometimes I get too excited out on the field. We've talked about it at length and I will be trying to do that this week. I just can't wait to get out there."

Fitting in with outside centre Ma'a Nonu would not be an issue because the side had been training in mixed roles all campaign. Williams does not think the situation in the World Cup could be compared with other areas of his career, admitting pressure is involved wherever he is playing and the requirement is always to concentrate on doing the little things well.

"You've got to prepare the boys the best that you can and that's what I try to do week to week," he said.

He also expects a physical battle with the Tongans, adding: "The boys will be coming at us with that physical intensity but we give as good as we take and that's the mindset we've got to be in this week because the island boys, when they play, come with that physicality and that's what we've got to match."