Chelsea manager Thomas Tuchel has put his hand up for allowing Real Madrid winger Vinicius Junior plenty of space to run at Stamford Bridge.
The Brazilian tormented Chelsea's back three in the first half as Real ran out 3-1 winners.
Asked if he had make a mistake playing Andreas Christensen in a three and leaving space down the left against Vinicius Junior, Tuchel replied: "Yes, it is my mistake."
Chelsea have now conceded seven goals in their last two matches, and Tuchel is struggling to understand why.
He continued: "If we have the same talk five days ago, we will still speak about the same defensive performance. In five days, it is seven goals conceded and we didn't change anything: not from the approach, line ups, or the system.
"I don't think there's a deeper reason for it. It is alarming. In two games, seven goals, but nothing has changed."
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