Having been out of the picture for the Tri-Nations defeat to Australia, Williams looked destined for few chances at the tournament.
However the 26-year-old was the surprise inclusion at inside centre - with Williams partnering Ma'a Nonu in the midfield.
And the former Toulon centre is excited to start the tournament.
"I want to take it in two arms and really give it a good crack," he said. "That's what I am aiming to do and am really excited to be playing.
"We want to start off with a good bang and I am thankful I am part of it."
Williams is expecting a full-blooded affair to kick-off the tournament, with Tonga looking to upset the hosts.
"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," he added.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.