A number of Chelsea players are in quarantine after returning from their summer break.
A group of the Blues' first-team squad are following government guidelines on self-isolation, the PA news agency understands.
People visiting countries not on the government's travel corridor list have to stay in isolation for 14 days on their return to the UK.
Chelsea are back in training and building towards the new Premier League season, with the Stamford Bridge men facing Brighton at the Amex Stadium on Monday, September 14.
The quarantine period will prove a disruption to manager Frank Lampard's pre-season plans, with the Blues still working hard on recruitment off the pitch.
England left-back Ben Chilwell has completed his £45million switch from Leicester, while France Under-21s defender Malang Sarr and Brazil centre-back Thiago Silva are understood to be close to completing moves to Stamford Bridge.
