Picked at 54 in last year's rookie draft, 18-year-old Williams has rocketed through the ranks courtesy of some strong performances in the reserves, leading to his elevation this week to the senior list.
An athletic half-back from Narrandera in southern NSW, Williams has been named among the best in three of the reserves' four games this year, giving him an opportunity to show his talents at senior level.
He is the first player from the Giants' academy, which was set up at the start of 2011, to make his senior debut for the club.
"It was a big shock to me, I wasn't expecting to actually get elevated from the rookie list just yet," Williams said.
"I was doing pilates with my group and Leon (Cameron) pulled me aside and told me to come into Sheeds' office for a chat and I had no idea what it was about.
"They were both pretty quiet and then Sheeds said 'we're going to play you against Gold Coast this week'.
"It was an unbelievable feeling. I rang mum yesterday and think she had a bit of a teary moment.
"We've been working towards this ever since I was 15 or 16."
At the other end of the scale, 29-year-old Thornton will make his first appearance in orange and charcoal following 11 seasons with Carlton.
The fourth oldest player on the GWS list, and second most experienced behind Chad Cornes, Thornton kicked eight goals in the reserves last week.
Small forward Devon Smith returns from a one-game suspension to face the Suns, with Lachie Plowman earning a recall and fellow key position prospect Adam Tomlinson selected for his first game of 2013.
There are some intriguing omissions, with key defender Stephen Gilham dropped for the first time as a Giant, following some indifferent form over the first four rounds.
Liam Sumner, Sam Frost, Anthony Miles and Jacob Townsend have also been dropped.
Williams' elevation and Thornton's GWS debut made for uplifting stories after teenagers Jono O'Rourke and Kristian Jaksch both suffered injury setbacks this week.
O'Rourke, the second pick in last year's draft, had overcome some hamstring problems to start his GWS career in the reserves, but suffered a broken jaw in last week's NEAFL game against Belconnen.
The 19-year-old will have surgery on Friday and is expected to miss the next six weeks.
Jaksch, pick 12 in the draft who has been kicking plenty of goals in the seconds, sustained a partial tear to his medial meniscus and will also be out for six weeks.
In better news, ruck prospect James Stewart has recovered from a back injury and is available for selection and Dom Tyson should be free to play in three weeks following his pre-season knee surgery.
James Dampney is a reporter for AFL.com.au. Follow him on Twitter: @AFL_JD
