Forwards coach Robin McBryde says it is imperative Wales start well against Australia at the Millennium Stadium on Saturday.
The Welsh got off to a terrible start against New Zealand last weekend, albeit badly hampered by the loss of three players to injury, and were 33-0 down with less than 10 minutes of the second half gone.
However, they improved after that, eventually losing 33-10, and McBryde says they will need to reproduce that second-half form if they are to salvage a solitary win from their autumn programme by beating the Wallabies.
McBryde said: "We are playing against the second best team in the world and we are going to have to be at our best.
"We've really got to start the game in the best shape possible to give us any opportunity of winning.
"We just left ourselves a bit too much to do after the first half against New Zealand. The scores were level in the second half and we need to start in that same vein of form.
"The character and resolve we showed to get back into the game (against New Zealand) was outstanding. We've got to take a lot of heart from it and hopefully build on it."
Wales boss Warren Gatland has put the announcement of his team back until Thursday lunchtime so that some key players have extra time to recover from injury.
Lock Bradley Davies and prop Aaron Jarvis are definitely out and centre Jamie Roberts, wing George North, lock Ian Evans and flanker Ryan Jones could be touch-and-go.
"We are going to give some players as much time as possible, so we are looking at Thursday, really," said McBryde on Tuesday.
"Ian Evans took a part in training this morning, which was a positive, but we are not forcing anybody. Thursday will be the important day for us."
Strength in depth
He added: "It is something we've had to deal with all the way through the autumn, really. We had a number of injuries coming into the series, so we always knew it was going to be a bit of a test of strength in depth.
"It's not ideal and it does affect the consistency within the squad but, having said that, it has provided one or two others with a great opportunity, players like Liam Williams, Aaron Shingler and Scott Andrews.
"I thought Scott Andrews, considering he has not had that much game-time this season, was able to lay a platform at scrum-time against New Zealand.
"He was up against a formidable opponent in Tony Woodcock, and Andrew Hore is known as a scrummaging hooker, so to come out of that test in a positive manner was hugely encouraging. And Scott was hugely effective in the loose as well."
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