Borussia Monchengladbach are growing increasingly pessimistic of keeping hold of Andreas Christensen.
The Dane is in the second season of a two-year loan with Gladbach.
Club chief Max Eberl has stated they'd be willing to break their transfer record to sign Christensen permanently.
However, on Monday he warned: "It will be a difficult task but I am hopeful that we can do it. We probably will not buy him, but maybe there is another way."
Meanwhile, Christensen said: "If I can start games for Chelsea, I will go back."