England's chances of qualifying for the semi-finals virtually ended on Saturday when they crashed to a six-wicket defeat against their Ashes rivals in the day-night game.
This was their second successive defeat in the four-team Group 'A', having already lost to India in the opening match. They will now clash with the West Indies in their last league game at Ahmedabad on October 28.
India and the West Indies have one win apiece from one game, and Australia one from two matches.
"We took this match in isolation, as a must-win game for both the sides to stay in the tournament," said Flintoff.
"One thing in the build-up to the game was people trying to link it to the Ashes series, but the Ashes start (in Brisbane next month) when we go to Australia."
England were comfortably placed at 83 for no loss before being dismissed for a paltry 169. They then grabbed three early wickets before running into Damien Martyn, who steered Australia to victory with a solid 78.
Flintoff conceded his young side needed to improve considerably if they wanted to give a good account of themselves in coming months.
"It is an exciting time in one-day cricket .. first Australia and then the World Cup (in the Caribbean next year). But we need to improve," said Flintoff.
"It is a young side. We have to step up as a team if we have the aspirations of doing well later in this winter."
Australia captain Ricky Ponting said he was not worried about ace fast bowler Glenn McGrath's indifferent performance against England.
The Aussie paceman gave away 27 runs in his first four overs before coming back strongly to finish with 2-36 off nine overs as a first-change bowler.
"You don't end up having a lot of concerns about one of the greats of the game that Glenn is. He delivers an honest performance every time he takes the field," said Ponting.
"He is fulfilling a different role at the moment -- bowling first change, something he has done for only half-a-dozen times in his career. So he is probably still learning the role."
Ponting lauded pacemen Shane Watson and Mitchell Johnson, and middle-order batsman Martyn, saying the trio did a commendable job.
"The bowlers did a tremendous job in the middle of the innings. Watson and Johnson were outstanding," said the Australian skipper, whose team were under pressure after losing to the West Indies in the opening match.
England made an impressive start before floundering against Watson (3-16) and Johnson (3-40). Martyn then completed the job under lights with a fluent knock after Australia had been struggling at 34-3.
"It was a great performance. We did not get off to a great start with the ball or bat and it ends up being a very comfortable win. We have worked hard from the time we have been here," said Ponting.
Australia will clash with India in their final league game at Mohali on October 29.