The Argentine was dismissed for a second yellow card with the score at 1-0 with 12 minutes remaining after City had a strong penalty appeal waved away when Edin Dzeko appeared to have been felled by Gerard Pique.

Vincent Kompany and Dani Alves rounded off the scoring in the final couple of minutes, but the damage to the visitors' chances of going through had already been done as Lionel Messi killed off the tie with the opening goal 23 minutes from time.

"I don't know why he sent me off. It was a clear penalty and the referee is two metres away from the incident," Zabaleta said.

"There was a clear foul on Dzeko too in the build-up to Barca's first goal, which he gave as a free kick to Barcelona.

"In the heat of the moment I ran towards him, but I didn't show any lack of respect because I couldn't say anything given I was on a yellow card."

Defeat means City bow out of a second competition in four days having suffered an embarrassing 2-1 defeat to Championship side Wigan Athletic in the FA Cup on Sunday.

However, Zabaleta said they had shown enough in their performance at the Camp Nou to suggest they stand a real chance of winning the Premier League title for the second time in three years.

"It was a very even game. They had good moments and so did we, but the team that makes the most of their chances is the one that deserves to win, so in that sense it is a fair result," he said.

"We are obviously hurt to go out because we are a team that aspires to win every competition, but that is football.

"Now we need to reduce the gap in the Premier League. We are nine points off Chelsea but we have three games in hand."

- Aguero hamstring strain -

Barca have also suffered on the domestic front of late as they have fallen four points behind Real Madrid in La Liga thanks to three defeats in six games.

And coach Gerardo Martino is hoping beating a team of City's calibre will re-energise his team for the final two months of the season.

"It is clear it hasn't been an easy week, but it is also true that our opponent could have gone much further in this competition. We had to suffer, but that is why you live for the Champions League," he said.

"They were two very hard games and we won them both. That means the players have done well collectively and individually.

"It wasn't just about going through, but to do so in the manner we did. That could strengthen us for what is to come, but the league still depends on how we react."

There could be more bad news to come for City as their top scorer this season, Sergio Aguero, had to be replaced at halftime due to hamstring strain and will undergo a scan on Thursday.

"I felt something in my left leg in the run with Messi at the start of the game," said the Argentine.

"I tried to continue, but at halftime I didn't want to run any more risks."

City assistant boss Ruben Cousillas said he was hopeful the injury would not keep Aguero out for much of the title run in.

"It is still too early to say how long he could be out. Apparently it is nothing serious," he said.

"He will have a scan tomorrow. The doctors will decide, at the moment we can't speculate."

Cousillas was on the touchline as manager Manuel Pellegrini was serving a UEFA ban for criticising referee Jonas Eriksson after the first leg and he hailed his side's performance in difficult circumstances.

"We are frustrated. We played a great game against a very difficult opponent," he said.

"We had our chances, but when you are left with 10 men it is always very difficult.

"After just eight months at the club we have our first trophy, which is important. Last week we were in four competitions, now there is just one left.

"We showed tonight that we are sill alive and we are going to fight for the Premier League."