Triple Crown hero Williams aims to make the most of starting spot against Australia.
Triple Crown hero Scott Williams is determined to grab his chance at centre stage on Saturday. (KO 11am UK time)
The Scarlets midfield ace had to contend with a place on the bench during the Six Nations, with Jamie Roberts and Jonathan Davies established as the central axis.
But Williams played a super-sub role and scored the famous match-winning try at Twickenham as Wales clinched the Triple Crown.
Now, with Roberts ruled out with a knee injury, Williams hopes to replicate his Triple Crown form from the outset against Australia.
"I'm just really happy to have the opportunity to start a game," said the 21-year-old. "I've played a lot coming off the bench, with Jamie being in great form.
"This is my opportunity now and I will do my best to try and take it. It's my big chance on the weekend."
Williams, who will win his 13th cap in Brisbane, was selected ahead of James Hook and Ashley Beck. He will form an all-Scarlets midfield with Rhys Priestland at fly-half and Jon Davies at outside centre.
He reckons the familiarity will be a major advantage but insists Wales face a daunting challenge against a wounded
"I think it's an advantage because we've trained and played a lot together," added Williams. "We are used to each other.
"We know we are going to have our work cut out. Australia are not going to be a pushover. They had a really scrappy game against Scotland and were unlucky there.
"But we are just concentrating on what we are taking into the game now. We have got a massive opportunity to put a stamp on a southern hemisphere side."
As the countdown continues for RWC2015, Tournament Chief Executive Debbie Jevans visited the Millennium Stadium to discuss preparations for the eight matches and reveal the positive news that 100,000 tickets for games at the home of Welsh rugby have sold in the last seven days.
Jason Harries is targeting a first win on the World Series circuit this season with Wales. The series returns to action this weekend in Dubai where Harries is part of a team hoping to build from its efforts in round one in October.
Wales skipper Jevon Groves says his side have addressed a few points from Gold Coast and aim to 'hit the ground running' in the next two rounds of the World Series, kicking off with this weekend in Dubai before heading off to South Africa next week.
Wales Sevens manager Steff Thomas is hopeful his side can build from a quarter-final spot in the opening round of the World Series in Australia when his side take part in the forthcoming double header in Dubai and South Africa.