Kalidou Koulibaly missed training on the eve of Chelsea’s Champions League game against RB Salzburg.
The defender missed Saturday’s 1-1 draw with Manchester United, having picked up a knee injury during the recent derby against Brentford.
And he did not take part in Monday’s session, indicating that he will not be available for the trip to Austria.
Chelsea are already without Reece James, N’Golo Kante and Wesley Fofana, who are all out injured.
Blues boss Graham Potter is expected to give an update on Koulibaly at a press conference this evening.