Reece James will not require surgery after picking up a hamstring injury in the Brighton game, The Telegraph's Matt Law reports.
However, the right-back is expected to be sidelined for six to eight weeks.
It means that the 22-year-old will certainly miss the games against Liverpool and Man City, as well as three matches with Tottenham, in January.
He might also miss the start of the Champions League knockout stage on February 22 when the Blues take on Lille.
James' injury has further strained an already depleted Chelsea backline. Ben Chilwell is ruled out for the season, while Andreas Christensen and Thiago Silva have issues of their own.
Source: Matt_Law_DT @ Twitter