Manchester City's Sergio Aguero celebrates after scoring during their Champions League round of 16 first leg soccer match against Barcelona in Etihad Stadium in Manchester, Feb 22, 2015. [Photo/Agencies]

Sergio Aguero rewarded City for a vastly improved second half showing with a clinical strike 20 minutes from time.

But with City down to 10 men after Gael Clichy's red card for a second booking, the majestic Messi had the chance to restore Barcelona's two-goal lead but his penalty was saved by Joe Hart and the Argentine headed the rebound wide.

"We are very happy with the result and even if it was 3-1 the tie would still be open," Barca coach Luis Enrique said. City midfielder Samir Nasri said in the build-up that while Messi played football from a different galaxy, the rest of Barca's squad shared the same planet as City's.

It did not look like it in a horribly one-sided first half in which Barcelona's entire ensemble were light years ahead in speed and movement.