The two sides are part of the so called 'Pool of Death', which contains four of the teams in the top nine of the world rankings, and defeat tonight would be a huge blow to their chances of making the quarter-finals with Australia lying in wait.
And Biggar, who made 16 appearances in the GUINNESS PRO12 last season, said: "We're trying to prove to everyone who has written us off that we've got a good shout in this game.
"We know what's at stake, but we are just concentrating on making sure we've got our roles all ticked off and everything else will take of itself.
"We're genuinely thinking it's just a game of rugby. It is 15-a-side and the pitch dimensions are the same."
Wales started their World Cup campaign with a 54-9 win over Uruguay, having already seen England also pick up a four-try bonus point thanks to their 35-11 victory over Fiji.
Much of the build-up to tonight's contest has been dominated by Stuart Lancaster's decision to start Owen Farrell at fly-half and Sam Burgess in the midfield.
"We've had a couple of days to get used to that with it being leaked out on Tuesday," GUINNESS PRO12 star Biggar added.
"Jonathan Joseph's injury has made them reshuffle a little bit. The two centres they've picked are extremely talented players in terms of physicality, and defensively they're going to be very strong and Owen will strengthen that.
"Both Owen and George [Ford] are superb players and I suppose it was the flip of a coin to decide who got that shirt.
"It'll be a physical challenge around that area and we'll just concentrate on our ten, 12, 13 rather than worry about their ten, 12, 13."
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