The Irish battled in subduing the USA 22-10 at New Plymouth on Sunday, the relatively narrow win coming after a disappointing Six Nations tournament in which Ireland lost to Wales and France, and only just beat Italy and Scotland - although their 24-8 victory over champions England in Dublin was a high point.
Murphy's backline colleagues came in for particular criticism for their poor handling in difficult conditions in their World Cup opener.
Keith Wood, the former Ireland captain, told the BBC: "They didn't seem to get off the ground at all and it was reminiscent of past World Cup failings.''
Of course, all that will be forgiven if they can sneak a win over the Wallabies and that is something Murphy is confident can happen despite a lack of compelling form.
"The belief in our backline is that we've got some fantastic players and that we can go toe to toe with anyone. In saying that, there's no point in shooting my mouth off too soon so we'll see,'' Murphy said today.
Ireland's team list will be released tomorrow afternoon. They have talent in the form of captain Brian O'Driscoll, in-form wing Tommy Bowe and solid first-five Ronan O'Gara, but fullback Murphy will be busy preparing for a difficult night defensively against Australia's backline if he gets the nod.
"They're awesome right across the board,'' he said.
"Australian rugby for a lot of years has produced fantastic inside and outside backs. They're fantastically talented and great players at breaking teams down and they're not bad guys either so they're thoroughly dislikable,'' he quipped.
"They are one of the most if not the most potent attacking backline in the world. They've got pace and power and they're intelligent footballers to boot. They have the works. They're renowned for being great attacking footballers so we'll certainly have our work cut out for us.''
If Murphy is as quick with his feet as he is with his wit, Ireland should be well covered at the back. In referring to Wallabies' wing James O'Connor, Murphy suffered a slight lapse from which he quickly recovered.
"Matty O'Connor, sorry James O'Connor - I was thinking of my Leicester coach and I'd be happy if he was playing to be honest, he's a few stone heavier. James O'Connor, he's a fantastic footballer as well.''
James O'Connor is likely to play a starting role against Ireland in tandem with talents such as Will Genia, Quade Cooper, Adam Ashley-Cooper and Kurtley Beale, with Ireland backs' coach Alan Gaffney, an Australian, paying particular attention to Cooper.
"He's a player who has developed very well over the last 18 months,'' he said. "He shows that he's got a lot more maturity in the way he plays the game. He's got exceptional skill levels and fantastic vision and obviously very good pace.''
Ireland flanker Stephen Ferris, who played his first World Cup game on Sunday, said nerves might have been a factor against the USA but they shouldn't play a part now the first game is out of the way.
"The legs felt really heavy for the first 15 or 20 minutes. I'm not sure what it was, a few of the lads were saying the same.''
Ferris said of the criticism: "Everybody's entitled to their own opinion I suppose, but we firmly believe that the group we have over here can definitely turn over any team on a given day.''