"All teams are equally good but I think world champions Australia are going to be the toughest of all," Middleton said after a practice session.
"We have been training for three days now and have one warm-up match against The Netherlands. Today we practiced on our defence and tried out a few variations along with team combinations. The team is young in terms of dynamics."
England are placed along side Australia, Pakistan and Belgium in Pool A of the eight-nation tournament while Pool B consists of hosts India, Germany, Netherlands and Argentina.
"We have been here for seven days now and the team is well acquainted with the pitch and the weather at this time.
"Everybody in the team is fit and in a good frame of mind. We are all set for Saturday when we play against Argentina in the first match," he said.