Chelsea goalkeeper Petr Cech thinks that the Blues need to stop making the "same mistakes" in order to improve their season.

The former Premier League champions have slumped twelve points below league leaders Manchester City, and are facing an early exit from the Champions League after a 2-1 defeat to Bayer Leverkusen on Wednesday night.

"We have been talking recently about the same mistakes - concentration and little details when we don't go to clear the ball," Cech told the club's official website. "I think we need to be much more aggressive in terms of defending and we get punished all the time.

"There are no excuses. We need to look first at ourselves and then we can criticise the other people because we put ourselves in the situation where we were 1-0 up [against Leverkusen] and we could have killed the game off.

"Then there would be no discussion whatsoever about things that were happening in the game. We have to take it like that and make sure that this is the last time it happens."

While Andre Villas-Boas has come under scrutiny for his managerial tactics, Cech thinks that the blame should rest solely on the players.

"The manager is not on the pitch, we are on the pitch and we are making mistakes," he added. "He cannot do anything about individual mistakes while he is standing by the bench.

"So the players are to blame and we know it and we try to make things happen and change. It is not easy but we keep going."

The Blues host Wolverhampton Wanderers at Stamford Bridge this weekend.