Devastated. There's no other way to describe how I felt last Saturday night after the final whistle brought an end to England's defeat by Wales. It was a massive opportunity missed, leaving England in danger of missing out on the knockout stages of their own tournament. A truly terrifying prospect. And not just for the English.

All is not lost though. As this week has progressed, belief in England has grown again. They are more than capable of beating Australia at Twickenham, galvanising a nation's hopes in the process. It's a close call, though, and key battles which will determine the outcome.

Let's start where it all begins: the set-piece. England have traditionally had a strong set-piece which has allowed them a solid platform to build on. In recent times it has come unstuck and has seen them under real pressure. A potent example was made in Paris by the French pack during the warm-up games. England disintegrated.

They can't afford to be anything but their best against Australia. The ongoing inquest into Joe Marler's technique at scrum time is a sideshow. Making a point about propping at an angle is nothing more than Australians trying to get an edge. They know the importance of the scrum and if they can place a seed of doubt in Romain Poite's mind going into the game, they will be happy. It might lead to a crucial penalty. If you analyse every scrum, illegalities are rife, sides are always trying to push the boundaries and gain an advantage.

Australia have improved in their set-piece and coach Michael Cheika will be happy with where he finds his team now. Hopefully a week of intense focus will mean that England have found their mojo and dominate in this area. It's about time.

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A key focus for both sides will surely be the breakdown. With David Pocock and Michael Hooper both having been selected, it will be close to a nightmare for England. Pocock has forced five turnovers to date in the tournament and will no doubt have a close eye on the ball on Saturday. Chris Robshaw and Tom Wood have a massive job on their hands to keep the Australian captain at bay. Let's face it, he's a massive pain in the backside for the opposition, which justifies his selection. He slows attacking ball and creates fresh turnover ball for his side, the best to surprise teams with by launching counter-attacks. Every side would want a player like that in their side, every side wouldn't want to play against one.

Hooper has a slightly different game and spends more time further from the breakdown. His tackling is more offensive and he regularly makes "ball and all" impacts. He has the pace to surprise attackers by jumping out of the line. It's an art that not many players can master. Hooper has done and England will need to be aware of this when carrying the ball into contact. If he makes a dominant tackle he makes Pocock's job much easier. Getting in on the ball quickly is far more simple in a dominant situation. It's not just in defence where Hooper can make a difference though. He is comfortable in the wider 15-metre channels and is a decisive runner with real pace. Great for Australia, but he is one player who can be a thorn in the side for England with or without the ball.

There are fascinating match-ups all over the field; Mike Brown v Israel Folau, Jonathan Joseph v Tevita Kuridrani, Robshaw v Hooper and Dan Cole v Sekope Kepu. It's going to be an incredible game. Australia like to move the ball about and I hope that England decide that playing that way is their best chance of winning, too. They did so for 40 minutes last week against Wales -- just as I had written in my column pre-match -- and it worked. Had they continued, I'm convinced the scoreline would have been in their favour.

Owen Farrell can (hopefully) have another good game, bringing the likes of Anthony Watson, Jonny May and Joseph into the game. The more touches they have the better chance England have of winning. Joseph coming back into the fold will be huge for Lancaster, I would like to have seen him with Sam Burgess as Brad Barritt seems to be doing less and less, but England's outside centre is a genuine threat to the Aussies. Nothing can beat outright pace and he's got that in abundance.

It would be catastrophic for England to lose this game. Exiting the World Cup at the group stages is not worth thinking about. It would have a massive impact on the tournament, I think. Let's everyone get behind England. Even you Scottish, Welsh and Irish. The competition won't be the same. Trust me!