Cancer survivor Lealiifano said it's "hard to say" if he is ready for that sort of load after having been carefully managed through the pool phase of the tournament.

Coach Michael Cheika this week indicated the 32-year-old had the inside running to take the problematic playmaking role in Saturday's quarter-final against England in Oita.

Cheika indicated Lealiifano hadn't played there more because of the need to cater for his wellbeing.

Bernard Foley started against Wales and Matt Toomua against Georgia last week, sparking criticism that the Wallabies were suffering through rotating the most important link position on the park.

Such methods may continue into the knockout phase after Lealiifano revealed his health is a day to day proposition.

The Brumbies veteran was asked if he felt ready to play three consecutive games.

"It's hard to say. As we've gone, it's just been managing each game as we go and seeing how I feel day to day," he said.

"I guess I'd be confident to if I was called upon but I think it's just about coming back to a week-by-week case and seeing how they go."

Lealiifano took a year off rugby after being diagnosed with leukaemia in 2016.

He was one of the stars of Super Rugby this year, steering the Brumbies to Australian conference honours.

Lealiifano started all 18 games and played more minutes than any player in the entire competition aside from his teammate Tom Banks.

That load may have caught up with a player who has been given a different regime to his teammates in Japan.

Strength and conditioning coach Brad Harrington revealed early in the tournament that Lealiifano was faster and stronger than earlier in his career but faced challenges in terms of recovery time.

"It's just probably the intensity of the game takes more out of him and he's getting older too, so we've got to manage our older athletes a little bit differently," Harrington said.

"That's the sort of balancing act with him but it's something that the Brumbies did really well this year and we've learned a fair bit off them."

Lealiifano said on Tuesday that he was grateful at the flexibility afforded him.

Australian Associated Press