The whole problem this season for Liverpool is that Van Dijk is not playing. it is a big mess in their defense every game.
Van Dijk is a key player in the defence line and his absence among other players made Liverpool looks miserable in different leagues. Klopp mission right now is to join CL (or EL) next time.. maybe.
Certainly... Liverpool are missing their two centre-backs who were quite good than what they have right now. Right now Kabak and Philips are adapting and learning things and they are not that perfect yet. Van Dijk plays a major role in defense and his absence sure his hurting them as there is no real leader in defence line to lead them properly. ]
Today they have game against Aston Villa and they surely want to make up for the humiliating loss they faced last time. But they also have the leg game in which they need to cover deficit so lot of things must be going inside the head of Klopp.