Glen Johnson has urged Chelsea not to let Antonio Rudiger and Andreas Christensen leave the club for nothing at the end of the season.
Both centre-backs are in the final year of their contracts at Stamford Bridge, despite both becoming valuable assets since Thomas Tuchel took over in January.
It means Chelsea are facing the real prospect of losing the duo, who both played in May's Champions League final win over Manchester City, unless they can be tied down to new deals.
Former Chelsea defender Johnson has said that it would be a 'disaster' for the club to let them both go.