Wales head coach Warren Gatland is not due to announce his starting line-up for the Rugby World Cup group decider against Australia until Thursday, but it would be no surprise if he made changes following last week's punishing encounter against Fiji.

Top spot in Pool A -- and a potential quarter-final clash against Scotland or Japan -- will be up for grabs in next Saturday's Twickenham encounter.

The losers are likely to face a last-eight appointment with South Africa, so stakes are high, despite both teams having already progressed from a so-called pool of death that claimed host nation England as its major casualty.

"We just have to assess how battered these players are and where there bodies are," Gatland said. "We need to decide whether we put them in next weekend or keep them for the following week.

"We will look and see what happens over the next couple of days in terms of selection.

"We do have other options, and depending on what style of game we want to play and what sort of game-plan we want will influence us in terms of the few changes we do make.

"Potentially, whoever we do play in the quarter-finals -- whether it's South Africa, Scotland or Japan -- we have had some success.

"We lost in the last Test in Japan in 2013 when I was on Lions duty. But we have had pretty good success in the last eight years against Scotland, and winning that game against South Africa last autumn was a huge milestone for us."

Flanker Justin Tipuric, who could be on course for a start against Australia, has no doubt how big a challenge the Wallabies' breakaway trio of Scott Fardy, Michael Hooper and David Pocock will present, although Hooper's participation could now be in doubt after he was cited for alleged foul play in the England game.

"It's a pretty special back row," Tipuric said. "Their number six (Fardy) doesn't get enough credit. He does a lot of the donkey work.

"Whoever plays there (back row) for them, they have strength in depth no matter what.

"The breakdown is a strength for them, and we need to make sure we look after that ball. You are up against the best with Australia, and it's going to be a good test."

Reflecting on Australia's 33-13 demoliton of England that sent Chris Robshaw's men through the World Cup exit door, Tipuric added: "Australia looked in control of it the whole time. They played to their strengths and their set-piece was on fire.

"I didn't expect that much of a margin, but we all know Australia's strengths.

"It showed in the game how good they were in the breakdown. I didn't expect their set-piece to be that good, especially the scrum. They were dominant. England are known for their set-piece, but Australia played really well."