Cheika: No comfortable feeling in Pool A
Pool A also includes hosts England, who beat Fiji 35-11 in the tournament opener on Friday, and Wales, who laboured to an ultimately convincing 54-9 win over Uruguay on Sunday.
"The teams in our pool will be having a totally different lead in," said Cheika.
"There is no feeling comfortable in our group. Perhaps that's how it should be. It's the World Cup and it will be tough every game and we will have to earn everything we get."
Cheika named Toulon playmaker Matt Giteau at inside centre and, for only the second time, stand-out openside flanks Michael Hooper and David Pocock in the backrow.
The strong team Cheika named is an indication that the former No.8 is taking nothing for granted, especially after Japan's shock victory over South Africa.
"You've always got to have that readiness in rugby because it's a contact sport. It's a game where the humble usually succeed," Cheika said.
"In any one contest, you might go good in one scrum and then you might get pushed off in the next one.
"You've just got to be on all the time. I think that all the teams who are coming here now more often – from what I've seen over the progression of the tournament – are believing that they can win, as opposed to coming here just to participate."
The Wallabies won the Rugby Championship last season, Cheika saying: "We were able to get a bit of consistency. We'll look now to push that to another level."
