Chelsea assistant boss Gianfranco Zola admitted the Blues’ performance against Derby left plenty of room for improvement after he named two players who failed to take rare chances to shine.
The Rams twice put the ball past their own goalkeeper in the first half to hand Chelsea fortuitous leads, first through Chelsea loanee Fikayo Tomori and then Richard Keogh, but fought back twice with goals from Jack Marriott and Martyn Waghorn. Cesc Fabregas eventually scored the winner shortly before the break as the Blues held on to win 3-2.
Despite the victory, Chelsea looked vulnerable at the back as Gary Cahill and Andreas Christensen – who have both had to wait patiently for their chance this season – struggled to make an impression.
“It was more than a little bit (shaky), especially towards the end,” Zola said. “A lot is down to them, they really played well, they surprised us.
“Gary played for the first time in a while. When we didn’t defend well, it wasn’t just the defenders.
“I thought Gary and Christensen could have done better with the ball in the first half.
“This is probably the complaint, but we will go through this and discuss this [with them].”
Maurizio Sarri’s side now face Bournemouth for a place in the semi-finals, while Chelsea are still unbeaten in competitive games this season.
Zola added: “Even today should’ve been a routine win. In this country, in cup games, they can’t be underestimated.
“We can call it a friendly draw, but Bournemouth is not going to be easy for sure.”