Chelsea assistant boss Gianfranco Zola was critical of Gary Cahill and Andreas Christensen after the Carabao Cup win against Derby.
The Blues scraped through with a 3-2 victory at Stamford Bridge to reach the quarter-finals, where they will be at home to Bournemouth.
Centre-backs Cahill and Christensen have both spoken of their frustration at being overlooked this season, but neither succeeded in making the case for them to be given a regular place.
Cahill’s mistake led to Derby’s first goal and both defenders looked unconvincing against Frank Lampard’s side. Christensen was replaced by David Luiz in the second half.
Zola defended the duo with regard to Chelsea’s sloppy defending – but pulled no punches in his assessment of their poor distribution.
“It’s fair enough to say that a player like Cahill, probably they play and then they don’t play for a while. Sometimes they might have a problem,” he said.
“Plus the way we play sometimes means our defenders are also exposed. It wasn’t only the defenders not defending well.
“I repeat, the way we play, everybody has to participate through the defensive phase and some things didn’t work.”
But Zola added: “I thought Gary and Christensen in the first half could have done better with the ball. Normally the distribution from the back is better than it has been tonight.
“That’s probably the complaint I can make about them. But we’re going to go through this and we’re going to discuss it.”
Cesc Fabregas’ first-half goal turned out to be the winner and came after Championship team Derby had twice equalised after going behind to own goals.
The first was from the Rams’ on-loan Chelsea defender Fikayo Tomori, who played against his parent club along with Mason Mount, and the second by Richard Keogh.
Derby threatened in the second half and almost scored a third equaliser when David Nugent hit the post late on.
Zola admitted that Chelsea were far from impressive, particularly at the back.
“It was more than a little bit shaky, to be honest, especially towards the end,” he said.
“To be fair, a lot is down to them because they really played well. They surprised us. They played with a lot of quality.
“A lot of it was also down to us because the passing wasn’t as sharp as it normally is.
“We certainly need to improve. It’s been positive in some ways but other things weren’t.”