Manchester City manager Manuel Pellegrini believes Barcelona were handed victory on Tuesday by the referee, Jonas Eriksson.
Former Malaga boss Pellegrini though argued in a post-match interview that the penalty converted by Messi should never have been awarded, claiming there was a foul by Sergio Busquets on Jesus Navas in the build-up.
“Of course I have a complaint, not only for the penalty and the red card,” Pellegrini said.
“I think in the whole match we didn't have a referee with impartiality to both teams.
“He decided the game. He decided the game because it was a foul by Busquets on Navas.
“The referee was three metres away and he didn't blow the whistle and after that the foul from Demichelis is outside the box, it's not a penalty.
“Important mistakes against a great team like Barcelona make it difficult to win.”
Pellegrini added that Eriksson should never have been put in charge of the tie as he has a chequered history with Barcelona dating back to their games against Milan a year ago.
“I think it is a mistake to nominate a referee that has had problems with Barcelona,” the Chilean continued.
“Maybe he made mistakes in Milan. To have the same the referee here, I repeat, is a mistake.”
