Defeat at Ajax on Wednesday night left City with just one point from their opening fixtures and five points behind second-placed Real Madrid.
However, Barry said that City can win their remaining three fixtures and have an outside chance of qualifying.
"The way the results have gone has made it tough but we have to try to win all three games and that would give us an outside chance," Sky Sports News quotes Barry as saying.
"We would have 10 points, and that is all we can do - it's a massive, massive task, but it is still there and we have to try to do it.
"It's not over yet. You can't just roll over when there are points available and we will give it our all to try to win all three games."
Their next game is at home to Ajax on November 6.