Chelsea boss Thomas Tuchel admits Reece James has received a setback in his efforts to return.
James is battling to come back from a long-term muscle injury.
Tuchel said, "We had a little setback because he caught the flu in the moment where he was very close to rejoining team training so this was a setback.
"Of course, it's too long for Reece and for all of us. We miss him a lot. I had the feeling right from the very start that we had to deal with a big injury and unfortunately my feeling was right.
"You always have a risk with a very physical player like Reece and a big muscle injury, that you have to consider there is a delay with the comeback, which is where we are right now.
"He's still in individual training, progressing a lot and doing almost everything you can do in individual training and we're waiting for him. The plan is that he rejoins the group next week."