City were beaten 2-0 by Barcelona at the Etihad Stadium in the Round of 16 first leg on Tuesday night, making it a very daunting task to head to the Camp Nou for the return bout with a two-goal deficit.
"Nothing is impossible in football," Zabaleta said.
"We still have 90 minutes to try to do something. We should go there and try as hard as we can.
"I think we must be happy with what we did in the second half with 10 men. Maybe Barcelona had more possession but they didn't create too many chances because we were very solid defending.
"Also we had chances to score and (Barcelona goalkeeper Victor) Valdes made a few saves.
"At the end of the day we must be a little bit disappointed but now we need to have belief and try to do well in Camp Nou."
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