Christensen has moved ahead of David Luiz in the Stamford Bridge pecking order following his impressive performances at the back for the Blues this season.
The Institute for Public Policy Research has called for the creation of a new customs union within which the UK would be able to opt out of EU rules in specific areas.
Reports say Klopp is planning for the second half of the season without the England international, who has only featured sporadically for the Reds this season.