Barcelona midfielder Sergio Busquets has criticised Manchester City following their 2-0 Champions League defeat to the Spanish champions.
City boss Manuel Pellegrini slammed the referee's performance after the game and could face disciplinary action.
However, Busquets believes that it is wrong to make excuses.
"Referees make mistakes all the time, for and against you," the Spanish midfielder told reporters.
"But making excuses for why you lose, is for losers."
Dani Alves, who scored Barca's second goal, has warned his teammates not to write off City ahead of the second leg in two weeks.