Zabaleta slams 'shocking' decisions
City headed into Wednesday's second leg of the last-16 tie at Camp Nou with a daunting 2-0 deficit to overturn, and were beaten 2-1 despite a much-improved display from their under-par showing at the Etihad Stadium.
The game was marred by a number of questionable decisions, with Barca not being awarded a first-half penalty when Joleon Lescott brought down Lionel Messi in the area before a Neymar strike was incorrectly disallowed for offside.
Messi scored midway through the second half to effectively kill the tie, but City were denied an opportunity to reduce the arrears when referee Stephane Lannoy waved away claims for a spot-kick after Gerard Pique appeared to foul Edin Dzeko.
It was that decision that led to defender Zabaleta's dismissal, the Argentinian seeing red for a second bookable offence after protesting vehemently to the official.
City captain Vincent Kompany did level matters late on, only for Dani Alves to respond immediately, leaving Zabaleta to fume at the performance of Lannoy.
"I was on the pitch but 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," he said.
"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.
"We tried from the beginning until the end, should have scored first and had more chances in the game."