They now face the 1996 champions Sri Lanka, and Prior admitted England have yet to hit top gear.
"We haven’t played our best cricket by a long way, but we are still in the quarters," he said.
"We have not even got anywhere near what we can do so there will be no pressure and we go into the match as underdogs against a very strong Sri Lanka team."
But Prior believes that if England do well in all three departments, they will be tough to beat.
"If we do come out and play as a team and get all our three disciplines right, we are going to be very hard to beat. As a team we are in a fantastic place," said Prior.
The wicket-keeper added that the win over the West Indies at Chennai last week, which saved them from elimination, was a morale-booster.
"That win gave us a huge amount of belief and a h