City travel to the Camp Nou on Wednesday needing to overturn a 2-1 first leg deficit if the Manchester club are to remain in the competition.
Manuel Pellegrini's men were completely outplayed by Barcelona at Etihad Stadium and City have since tasted defeat against Liverpool and Burnley.
Saturday's shock 1-0 loss at Burnley has dented City's hopes of retaining the Premier League title but Zabaleta believes a positive result in Barcelona can kick-start their season.
"We are going to play against one of the best teams in the world. It's not going to be easy, but nothing is impossible in football," the Argentina international said.
"You have to be ready for these moments. Things can change on games like this.
"You just have to move on to the next game and try to win it. That's what football is.
"It's good that the game [comes after] just three days. We need to recover well, go to Barcelona and see what we can do. Hopefully we can do it."
