Lack of leadership and experience
There is a clear shortage of leadership in the current Chelsea squad. Their talisman Eden Hazard, left them this summer. Moreover, Gary Cahill and David Luiz, two of Chelsea's stalwarts also departed. Now, only Cesar Azpilicueta is the only experienced player with leadership attributes left in the dressing room.
Due to the transfer ban, Chelsea has a squad full of young and inexperienced players. And trusting youth has its fair share of disadvantages. Developing the youth is an intrinsic process and the selection of right leaders is a must.
Chelsea's defensive department has only one true leader and that is Cesar Azpilicueta. Over the past couple of the seasons, his form has dwindled quite a bit and he hasn't really been able to adapt to the fullback role.
At times, he has looked vulnerable on the counter as he isn't able to backtrack quickly anymore. Hence, the backline has often looked volatile and unorganized due to the lack of effective leadership.