Wales look to take their chances against wounded Wallabies
The Welsh are in the box seat for a spot in the quarter-finals after surviving a huge scare against Fiji in their opening match then labouring to a 28-8 win over Portugal last weekend.
Australia are viewing Sunday's match in Lyon as a do-or-die affair after going down to the Fijians last weekend and King said Wales had to be better than they were against Portugal.
"Against Fiji we were really accurate but there were a few changes against Portugal and it was not quite at the same level. We have got to take our chances against Australia," he told reporters at the team camp in Versailles.
"If we get our discipline, accuracy, set-piece - every part of our game - spot on, we will be very a hard team to beat."
King said flanker Tommy Reffell, who came off the bench against Fiji and was a late withdrawal from the Portugal match, and Leigh Halfpenny, who started at fullback against the Portuguese, were struggling with injuries.
"Tommy is nursing a little leg injury, he is just being assessed and we'll know more in the next couple of days," King said. "Leigh Halfpenny is the same."
The injuries might not impact too much on the plans of head coach Warren Gatland, who is expected to revert to the players that beat Fiji when he names his team on Friday after giving some squad players a run against Portugal.
Victory for Wales on Sunday would secure them a place in the quarter-finals and King said they needed to trust in what they have been doing well when they take on the Wallabies.
"We might adapt a little bit but we'll stay true to ourselves," he said.
"Bringing the back three into the game as much as possible, trying to get control from our half-backs, the forwards providing good quality ball and making our defence hard to break down.
"We're trying to be better than the week before and challenge Australia in all those areas."
