Bernado Silva said Manchester City's performance was "unacceptable" after they slumped to a 2-0 defeat against rivals Manchester United.
City - entering the game 25 points off leaders Liverpool - were dealt an early blow, a costly Ederson error allowing Anthony Martial to give United the lead.
To compound to City's woes, Sergio Aguero had to be taken off with injury - a profound worry with Real Madrid travelling to the Etihad in just nine days.
The Premier League Champions pushed for an equaliser, but the absence of the injured Kevin De Bruyne was evident, Scott McTominay taking advantage of another costly Ederson error to wrap the game up in stoppage time.
Silva, speaking to Sky Sports after the game, acknowledged the mistakes were unforgivable and says they need to improve drastically.
"It was a bad game for us. Not acceptable. We didn’t start badly and were playing quite well until we conceded.
"We know how good the Manchester United players are on the counter-attack, very aggressive. So our performance was not acceptable.
"We will have to watch the game back and listen to what Pep has to say. But a team like ours cannot lose this many games. We need to check what’s not going right and try not to make so many mistakes."
When promoted whether City simply weren't feeling any pressure in the Premier League, Silva agreed. However, he maintained that such a performance in a derby was unacceptable.
"The reality is that the pressure is not on the Premier League. We don’t have the pressure as we know our position is probably not going to change.
It hurts because we wanted the title. Maybe that’s a thing, but it’s a derby, it’s an important game for our and it’s unacceptable to come here and play the way we did."
