Sapporo - Australia playmaker Christian Lealiifano is "holding up pretty well" after taking a pounding from Fiji during the hard-fought 39-21 win on Saturday, according to the Wallabies' strength and conditioning coach.

The fly-half, who celebrates his 32nd birthday on Tuesday, found himself on the receiving end of some heavy duty but legal tackles from the Flying Fijians and struggled to impose himself on the game, being substituted for the final quarter.

"He's holding up really well," coach Brad Harrington said of Lealiifano at Australia's team hotel on Sunday as the players recovered from the bruising opening encounter with the Pacific islanders.

"In his position, he goes to the line and the big Fijians didn't miss him last night (Saturday). He's pretty sore this morning," added Harrington.

That Lealiifano is featuring at a World Cup at all is a major achievement given the leukaemia survivor only made his Australia return last month after more than three years out of international action.

"You can't really challenge Christian's character and his work ethic, what he's been able to come through the last few years," said Harrington.

Australia flanker David Pocock, who will retire after the World Cup, played the whole 80 minutes against Fiji despite his recent comeback from six months out with injury.

"I am sure you know how meticulous he (Pocock) is with his prep," Harrington said.

"For him to come back and play 60-odd minutes against Samoa (in a warm-up game) and then get through the whole game (against Fiji) is a measure of where he is at.

"The way David views his prep is second to none. He is all over nutrition, sleep, his training. He's very engaged in it so, for us, it is quite easy to sit down and map out his week."

The resilience of Pocock and fellow back-row forward Michael Hooper, the Australia captain, has long been admired given they occupy two of the most physically demanding positions on the field.

"We get to see those guys every day," said Harrington.

"From the outside people say, 'wow, it's unbelievable how they keep playing and turning up every week'.

"But when you see what they put in, it's nothing flash. Sometimes the mundane and boring stuff is what sticks those guys out."

Two-time champions Australia, losing finalists at the 2015 World Cup, next play Wales in what is set to be the crunch Pool D clash in Tokyo a week on Sunday.

Harrington, who worked in Wales for six years, forecast another gruelling encounter for the Wallabies.

"I know those (Wales) guys pretty well," he said. "Physically they will be in great shape.

"They are good people, they work hard, train hard. They will be fit. It'll be a good game. Physically they have improved a lot."