Michael Ballack has revealed how Chelsea's players held a training ground inquest into the set-piece errors which are threatening to disrupt their season.
Ahead of Wednesday night's Champions League clash with Atletico Madrid, Chelsea are becoming increasingly concerned with defensive errors - that allowed Aston Villa to inflict a second successive away defeat on them last Saturday. Chelsea lost 2-1 with both goals being conceded from corners.
Ballack said: "We've spoken about the game, we've trained on set-pieces and special situations, but it's all about individual mistakes. That happens in football, but that's what we have to cut out."
Captain John Terry was furious with their defensive lapses and Ballack, who missed the game with an ankle injury, revealed the squad are determined to eradicate the mistakes.
"John's reaction on the pitch showed that he takes a big responsibility not just for himself but for the team," Ballack added. "He was really disappointed when we conceded the second goal.
"That's what you need, emotions like that, to make sure it doesn't happen again. We speak with each other. We have no problem criticising each other in the dressing room. A good team with strong players has to do this.
"We've done that, then we shake hands and get back on to the training pitch and try to do better.
"I wasn't involved, not in the team, but I know the problem. I was there the next day and we spoke about it. Everybody has to make an impact on the situation, me too.
"It's a little bit unusual to concede twice, which is why we were so disappointed after the game. We played well, which makes it all the more disappointing.
"We've watched the game on TV at Cobham. We saw who made the mistakes, and everyone knows that, but in football people make mistakes. We have to work on it because it's happened again on Saturday. It was just one game, but it was obvious we lost that game on set-pieces."