Warren Gatland spoke of his relief that Wales made it out of the "group of hell" and is now targeting top spot in Pool A.
Australia's comprehensive 33-13 beating of tournament hosts England at Twickenham on Saturday meant that the Wallabies and Wales qualified for the quarter-finals.
Before the tournament started many considered Wales as underdogs to make it out of a highly competitive pool, but their stunning 28-25 win over England last week proved crucial.
Head coach Gatland will not allow Wales to rest on their laurels, though, and believes his team can play with more freedom against Australia next Saturday in a fixture that will determine the pool winners.
"It was always our plan to make the quarter-finals. We knew how tough this group was going to be," he said.
"It's been the group of hell, not just the group of death. It's taken the shackles off and allow us to try and win the pool.
"With 15 minutes to go [of England versus Australia] it was like I was sitting in the box myself. I said to my wife what happens next changes people lives. I am just trying to take things in perspective.
"It [Australia's win] gives us the opportunity and we don't have the burden of needing to win the game to qualify."
Wales have had well documented problems with injuries, with Leigh Halfpenny, Rhys Webb, Cory Allen, Hallam Amos and Scott Williams among the lengthy list of absentees.
Gatland now has more issues to contend with, as Dan Lydiate has an eye socket injury and Bradley Davies has a broken nose, but the New Zealander says he is not tempted to make wholesale changes.
"There is no temptation [to rest players]. It's about picking the right team," he added. "We might change one or two players. We have not discussed selection."