"They were the ones to blink first and became professional after the last tournament. They've now got a four-year jumpstart on everybody else and we're all playing catch up. This World Cup is theirs to lose."
Soper says the last team to beat England was France – a team, which is living up to its reputation of being highly unpredictable.
"They play so unpredictably," says Soper. "They've cycled through about three or four different first five options in the last year or so. They've changed their coaching setup. Then they promoted an assistant coach to head coach. It was utterly bizarre... So we don't really know what they're going to up with at this tournament, which is very exciting."
England are currently ranked number one in the world, while the Black Ferns remain strong contenders at number two.
Asked whether the home-ground advantage will make a difference and give the Black Ferns an extra nudge, Soper says this is the great unknown in this tournament.
"It's an interesting one because the women in rugby aren't used to playing in front of a home crowd. And let's be honest, it's only been in recent years that we've started to see some awesome crowds turning up.
"It's an unknowable, particularly considering the numbers we're hearing about how many will turn up at Eden Park this Saturday. They're expecting around 35,000-plus. Hopefully, we'll see a sellout. But we won't know the impact that'll have because we haven't seen it before. That could be the lift that we need."
Despite the potential advantage the home turf might offer, Soper says this tournament is really England's to lose.
"I hate to say that, but it's the truth. They've set the world record of 25 wins, they've got a good programme and they've got the depth. They've been working for a long time, whereas we've had a lot of disruptions in our lead-up... That's not to say that if they slip, we won't catch them. But we're going to need to slip and we're going to have to pull off something outrageous."
History has, however, shown that the Black Ferns know how to win when it comes to the biggest stage.
"Our history in women's rugby is made of people doing outrageous things, of not waiting for permission and just going for it. If we are going to write a good women's rugby story, it would be that outrageous upset, but it would just be that: an upset for us to win."
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