"It is different. There is no question it is different. The game over here is a bit slower compared to Super Rugby," Giteau said on Fox Sports' Rugby HQ.
"As far as test rugby, it's really, really hard for me to say. The last time I played was in 2011.
"If I am chosen, if I am selected, I would love to be a part of it [but], I haven't played at that level [for a long time], so I don't know if I am up for it.
"That's probably the biggest question. I would certainly love to test myself and give myself every chance to have a go at it. But there is certainly no promises there."
The 92-test star's candid confession that he harbours even the slightest of doubts will add to calls for Cheika to ask Giteau - and possibly Mitchell - back for the Rugby Championship to assess their international form, rather than gamble on a straight-out inclusion in his 31-man World Cup squad.
"The season's about to be finished in a couple of weeks in France and so they'd be available to do that," former Wallabies captain George Gregan said this week.
Mitchell enhanced his claims for a test return with a slashing solo try to clinch Toulon's European Cup Twickenham triumph over Clermont.
The 63-test winger admitted he and Giteau received a congratulatory text message from Cheika but no promises on test selection.
"[Just about] his involvement in the European Championship and knowing how hard it is to win, let alone a few consecutively," Mitchell said. "Nothing further than that. I am still hoping I can get a bit of a ride on [Giteau's] coat tails."
- AAP