Chelsea midfielder Kai Havertz missed the 3-0 victory over Rennes on Wednesday after testing positive for Covid-19.
Chelsea confirmed the news before the game against Rennes.
The club said: “Frank Lampard has confirmed Kai Havertz has tested positive for Covid-19.
“As a consequence the player is now undergoing a period of self-isolation and is not involved in tonight’s Champions League game versus Rennes.”
According to the NHS guidelines, anyone who tests positive for coronavirus must self-isolate for at least 10 days.
Havertz will now miss Chelsea’s home fixture against Sheffield United on Saturday.
With football going into an international break after this weekend’s fixtures, Havertz could return for the Blues’ trip to Newcastle on November 21.
Havertz has scored four goals and provided three assists in 10 appearances across all competitions for Chelsea.