Michael Ballack has revealed that Chelsea's players conducted an inquest into their poor defending following the 2-1 defeat by Aston Villa.
Villa twice scored from set-pieces in Saturday's Premier League clash as the Blues slipped off the top of the table to be replaced by Manchester United.
Manager Carlo Ancelotti admitted his concern after the match and has worked hard in training this week to try and sort out the problems.
Ballack insists the players were just as disappointed with themselves and have spoken candidly about the issue over the past few days.
The German midfielder feels everyone in the team must focus on trying not to make any more individual errors.
"We have no problem to criticise each other in the dressing room. A good team and strong players have to do this," said Ballack.
"We have done this. After that we shake hands and go back on the training pitch.
"The way we lost was very disappointing. We watched the video of the match and everyone could see who made the mistakes.
"That is football, somebody has to make the mistakes. We trained on set-piece situations but it is all about individual mistakes.
"We have to work on it. It was just one game but it was obvious that we lost on set-pieces. We have to be aware.
"Everyone has to improve their movement and defensive organisation. It is a point of personal attitude. Don't concede a goal.
"It happens once now and hopefully it won't happen again. We have to focus on our strengths, which is playing good football and winning games."
Captain John Terry was visibly angry after Chelsea conceded their goals against Villa and Ballack hopes the rest of the players will learn that such mistakes are unacceptable.
"His reaction on the pitch shows he takes a big responsibility. Not just for himself but for the team. That is what you need, you need the players to see it can't happen again," Ballack added.
"I think I have to do this as well, not just because of my age. I have a few years behind me and I have been through a few situations.
"I have to speak to help the team, but not just me, everyone has to take responsibility.
"Of course the weaker teams in the league, they try to score against us from set-pieces because most of the time we will have more possession on the ball."