|Rugby World Cup: England v Wales|
|Venue: Twickenham Stadium Date: 26 September Kick-off: 20:00 BST|
|Coverage: Live on BBC Radio 5 live and sports extra, BBC local radio, plus live text commentary on every match on the BBC Sport website|
|Further coverage: BBC Radio Wales, BBC Radio Cymru, BBC Radio Scotland, BBC Radio Ulster and BBC Local Radio|
In his 2015 Rugby World Cup column for the BBC Scrum V website, former Wales captain and back-row Colin Charvis looks ahead to Wales' crunch clash against England and considers the potential weaknesses in the opposition ranks.
England's changes in the backline makes it a little bit more exciting doesn't it? Owen Farrell in at fly-half for George Ford and rugby league convert Sam Burgess replacing the injured Jonathan Joseph at 13.
It makes the Welsh preparation a little bit more difficult. They had probably prepared and anticipated what Joseph brings to the game.
Joseph is a big loss for England but the gain is that Burgess is a very, very strong runner and he will come route one at Wales. He's got a good fend and probably relies a lot on his offload a bit more.
When teams prepare for the World Cup they've got to have a Plan A and a Plan B, and it's quite weird that just those two selection changes suddenly may have Gatland and the Wales team thinking of attacking and defending a bit differently.
I'd been talking to my mates from England teams of yesteryear about how the current side hasn't got that superstar, that guy who can walk down the high-street in most cities and be recognised.
I don't know whether this is what Burgess could become; bringing him in could be an absolute stroke of genius, but I can't see Wales being naive in defence and letting him have a free rein.
He is a big player and mentality-wise he'll be fine with the occasion but... once you get into loose play and after three of four phases his positional play might have people wondering where he is and what he's doing.
He is then going to have people like Wales blind-side flanker Dan Lydiate stepping into his channel. Burgess can excel for Bath at club level but international rugby is very much different.
England had a rugby league convert when they won they 2003 World Cup in Jason Robinson, but you must bear in mind that he had already played for the 2001 Lions, scoring in his first Test.
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He was already a very well-established union player, there was never any doubt with Jason. He was on the wing or at full-back with an incredible turn of pace and one of the fastest players around.
Whereas Sam has only played Test rugby over the last couple of weeks really, and people have been questioning whether he is a back-rower or a centre.
You can't doubt his ability as a rugby player, but will it all boil down to positional play? He's in a pivotal position there, get in the three-quarters and a lot is expected of you.
I also would have thought that England would have stuck with Ford because he is a very good attacking option, I don't think he had a particularly bad game against Fiji.
Ford can also make his tackles and he does. He may not be as dominant and strong a tackler as Farrell, but I don't think you base your game around the concern that Wales are just going to run down that 10 channel again and again.
Wales can be confident
Before Gatland selects his team, we can be certain of at least 11 of the names that will be on the team sheet.
Wales play a certain way, know their own strengths and, if they can play to their potential, I can see them performing very well at Twickenham.
Wales' World Cup match against England is a one-off, and Warren Gatland and his players need to approach it that way.
I've faced England in a World Cup but, in hindsight, we might have been punching above our weight when we were beaten in that 2003 quarter-final.
That England team went on to become world champions, but the side is completely different now.
A lot of these Wales players have been to Twickenham and won, so they should be confident about Saturday's match.
England have home advantage and the psychological edge of winning at the Millennium Stadium earlier this year.
But Wales know what it takes to beat England. They outplayed England for the first 40 minutes in February - now they need to play like that for the whole 80.
Tipuric's time will come
Wales' back-row always generates a lot of debate, and Justin Tipuric's recent form has only intensified that talk.
He played as an open-side flanker against Uruguay - with captain Sam Warburton switching to blind-side - and he produced another fantastic performance.
The open, loose game suited Tipuric, and he showed that playing with Warburton can work.
But the England game will be different.
They will be much more physical, and it's going to take players with more bulk and power to stop them.
Gatland tends to be loyal in his selections, and I expect him to recall Dan Lydiate at blind-side and Taulupe Faletau at number eight, with Warburton reverting to open-side.
For Tipuric it's frustrating, but his time will come.
The game could open up and he could have a major impact from the bench. Whatever happens, he will have his chance at this World Cup.
Bridging the gap
If Wales' win against Uruguay was routine, the World Cup as a whole has been spectacular so far.
Japan's historic win against South Africa captured the imagination, and showed what you can do when you combine guts and determination with intelligent coaching.
It also opened the world's eyes to the fact that the gap between the top few nations and the rest is not as wide as we might have thought.
I actually watched Japan's dramatic victory in the only place on earth that was unhappy with the result: South Africa.
I was there to work on the opening round of matches but I'll be at Twickenham for Saturday's big match.
Wales' game against England is going to be a huge battle, and I wouldn't want to be anywhere else.
Colin Charvis was speaking to BBC Wales Sport's Dafydd Pritchard and Bruce Pope.