Chelsea are eager to receive offers for centre-backs Antonio Rudiger and Fikayo Tomori, according to ESPN.
Both players were close to leaving in the summer window, but ended up staying.
Frank Lampard has preferred Thiago Silva and Kurt Zouma as his central defenders this season.
Tomori has not played since September 29, while Rudiger has only three outings this season.
If they move in January, Tomori is likely to go on loan, while Rudiger could leave permanently.