The whirlwind of speculation may continue over who Wallabies coach Michael Cheika will settle on as his preferred starting halves combination for the World Cup in the UK.

But Bernard Foley has hinted that Cheika may not even settle on one combination from options that include himself and Quade Cooper at No. 10, halfbacks Nick Phipps and Will Genia and two others who can play at 10 - Matt Toomua and Matt Giteau, the latter also at halfback.

Speaking from Notre Dame University at Indiana in the US where the Wallabies are preparing to play the US Eagles in Chicago on Saturday, Foley said the combinations are still being switched in training.

"I don't know if it is ever going to be set," Foley said on Tuesday after Wallabies training.

"The way Cheik wants to play … I think it's a bit of a horses for courses mentality.

"We just have to get on with it and make sure that we make the most out of every day and every training session and try and gel with the combinations around us."

Foley said that life in the Wallabies camp has shifted up a gear now they are in the US preparing for their final Test before the World Cup, starting on September 18.

In the US it is inevitable Jarryd Hayne has been spoken of as the former NRL star also prepares for Saturday, when he learns if he has made the San Francisco 49ers roster of 53.

The Wallabies have enjoyed the buzz of American football by following Hayne's progress and from dabbling with some American style passes and throws at Notre Dame.

While focused on their Test against the USA Eagles, the Wallabies are right behind Hayne, said Foley, whose brother Conor has played American football as a member if the Australian team.

"I know a lot of people are talking about it. It's such a great achievement," Foley said. "Just [from] speaking to my brother about what transfers across, what skills …

"It's just amazing to see how well he has picked it up and how he has done it.

"The environment he is in is so cut-throat. When he is over here everything is under a magnifying glass. It's great for him to be going so well. Hopefully it continues."

Saturday's Test is the Wallabies' last game before their World Cup opener against Fiji on September 23.

"Everything we do now is leading towards that first game," said Foley

"This is our last trial and our last hit-out as a team and individually.

"Everyone wants to be firing and playing their best footy leading into such a big tournament."