"We had problems defending and we will try to improve this week," said the Chilean following City's defeat in Helsinki, Finland.
"If we buy someone, then OK. But, otherwise, we have a good squad. But, yes, we have conceded many goals, we will have to find ways to change this.
"You are always concerned when you are 3-0 down but we lost in pre-season.
"We did not lose three points and that is important. We will be at our best for the Premier League."