Thomas Tuchel revealed that Mateo Kovacic has tested positive for Covid just one day after returning to training following a lengthy hamstring injury.
The Croatian midfielder has missed the Blues' last eight games due to an injury picked up in training in October.
The Chelsea boss was expecting a boost to his squad ahead of the final Champions League group clash away at Zenit St Petersburg on Wednesday night, however Kovacic is now in isolation.
Chelsea boss Thomas Tuchel revealed that Mateo Kovacic has tested positive for Covid today
'Mateo was in training yesterday with a big smile and was pure pleasure to have him back,' Tuchel said.