Andreas Christensen has been widely expected to renew his contract at Stamford Bridge but after talks have stalled, Chelsea risk him walking away.
The Blues had opened talks with the defender but after a two-month standoff with no contact, an agreement has failed to be met, according to Goal.
The 25-year-old has become a key member of Thomas Tuchel's squad and his importance could increase with Antonio Rudiger linked with a move.
But his current contract is set to expire in June 2022, leaving him free to open discussions with overseas clubs from January 1.