City were knocked out in the last 16 thanks to goals from Lionel Messi and Dani Alves, but Zabaleta, who was sent off, says three key decisions did not go his side's way.
Zabaleta felt that there was a foul in the build up to Barcelona's first goal, that City deserved a penalty and he insists he should not have been dismissed.
"It was very clear - Pique came from behind and made the tackle on Edin Dzeko, and the referee was only two metres away. He saw that very clearly," said Zabaleta.
"It was also a foul against Dzeko just before Barcelona’s first goal. He held the ball and turned, and Pique had hold of his shirt, and the ref gave a free-kick to Barcelona.
"Sometimes in the game you are nervous because you are trying to get the result, and sometimes shocking decisions by the ref make you a bit angry.
"I don’t know why I got a red card because I went to him to talk in a good way. I was a little bit angry to him because he didn’t give the penalty but I was always respectful to him.
"I am very frustrated at the decision because it was a shocking decision. I am disappointed but also very proud of the team because I think we played a fantastic game."
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