Giteau celebrated his 100th cap with a man-of-the-match performance in Sunday’s controversial 35-34 victory over Scotland and now faces a semi-final appointment with Argentina at Twickenham.
The 33-year-old has benefited from coach Michael Cheika’s demand to the Australian Rugby Union that they reverse a long-standing policy by allowing him to pick overseas players if they have made 60 or more international appearances.
It has lured Giteau away from his Test exile at Toulon where he has been magnificent since his shock exclusion from the Wallabies’ squad at the World Cup in 2011.
“I never thought I’d be playing in a World Cup semi-final a year ago,” Giteau said. “I thought I’d be doing a couple of speaking gigs to get a bit of cash. That was the plan but it’s just been an amazing ride for me this last six months. We showed a lot of character at the end against Scotland. Personally, I’m just happy we survived another week.
“The 100th cap was good, but the man of the match award I think should have gone to someone else in our team. We take a lot from the way we regrouped, how calm we were when they scored a try with only four or five minutes left. We were able to get down their end and apply pressure. We took a lot of confidence out of that.”
Giteau will duel with Toulon team-mate Juan Martin Hernandez when Argentina attempt to reach the final for the first time on Sunday.
“Juan is very skilful, he’s tough, defensively strong and adds a lot of stability to that team,” Giteau said.
“I know what it’s like to play with him, especially in big games. He is a very, very good player. He’s very confident in what he does and the things he can do a lot of other players can’t.
“Argentina are very good at every World Cup. Whatever they do, they always seem to peak in these tournaments. They’re incredibly dangerous.
“We’ve seen what they were able to do to Ireland and how far they pushed New Zealand in the first game.
“Every round they’ve been really good. They’ve blown teams away quite easily.”