Williams will reach the milestone on one of football's biggest stages as Greater Western Sydney look to keep their season alive when they take on Brisbane Lions at the Gabba.

Williams admits he never thought he would play 100 AFL games.

"I actually never thought I'd play 50 games, let alone 100," Williams said.

"I guess this week I'll be having phone calls with Mum and that about how far I've come. I guess I will reflect on the days I was playing rugby, basketball and all those type of sports through school.

"I haven't really had time to think about that milestone just yet, just because it's finals time and I'm thinking about playing in finals and how exciting that is. I'm sure through the week I'll be able to reflect on that as well."

The 24-year-old is in his seventh season at the Giants, after being picked up with selection 55 in the 2012 Rookie Draft.

Williams said the 100-game milestone has been a while in the making after it took some time to establish himself in the senior team.

"It took me three years, I was in and out of the side. I'd play a couple of games, I'd come in and play sub and not play much but Leon (Cameron) always referred to it as you've got to do your apprenticeship, sort of thing, in those early days," he said.

"It sort of took me three years to crack into the side and play regularly. I had the hiccup with my achlles last year and before that I had a couple of good years where I felt like I was starting to take off but then had the hiccup.

"This year I've played 21 games now. I'm just glad that this year I've been able to travel with the boys and be around the boys and now I'm looking forward to this weekend."

Williams will run out for his ninth AFL final on Saturday night. This season has been a stark contrast to last year, where his first AFL game for the season was in the elimination final after suffering an achilles injury in the pre-season.

Williams said he much prefers his preparation for finals this year, although admitted the bye did come in handy.

"It's a big change. I think that week off before round one of the finals was huge because my body was starting to get a bit sore just because I missed the whole of last year with an Achilles injury," he said.

"I've loved being back playing, even that travelling with the team and being around the boys because last year I was in here, being monotonous with my rehab so it's a big change up, travelling and I've loved this whole year."