An upset on Friday evening could make qualification difficult for the hosts, who will also have to face Wales, Australia and Uruguay in a tricky Pool A.
"It's a huge game," the World Cup winner told Sky Sports News. "There's no other way of looking at it - it's a massive game. England have got to look at it as kind of like a quarter-final very early on.
"Fiji are a great team. They're ranked highly in the world, they've got speed, they've got power, they've got understanding, and they've also got guys that are really dominating European rugby over here and in the Super 15 as well.
"[They] need to be respected - will be respected - but for England, they've got to show that they mean business early on."
England have won all five of their Tests against Fiji.