More than four Chelsea players are self-isolating after testing positive for Covid-19.
The Daily Mail claim the club have confirmed there has been an outbreak of coronavirus among the squad after players travelled abroad.
Chelsea have not revealed the names of the players who have tested positive but the news has thrown Lampard’s pre-season preparations into turmoil.
The Sun claim Mason Mount, Tammy Abraham, Fikayo Tomori and Christian Pulisic are all in quarantine after returning from Mykonos in Greece.
It is not yet clear if any of the quartet, who went on holiday together, have tested positive for coronavirus, but they are self-isolating as a precaution due to the outbreak at Chelsea.
There have been 12 new Covid-19 cases at 14 different clubs since last week, with players jetting across the world during their short-lived breaks between campaigns.
Chelsea do not play on the opening day of the 2020/21 Premier League season and will instead travel to Brighton on 14 September.
Sheffield United, West Ham and Brighton have all been affected with positive cases.
Lampard hopes to have all his transfer business completed by the Brighton game and Chelsea confirmed the signing of Ben Chilwell on Tuesday.