Thomas Partey's manager Diego Simeone has tested positive for coronavirus.
The Atletico Madrid manager has no symptoms but is now self-isolating at home.
Los Rojiblancos returned from a training camp on Friday and Simeone's was the only positive result from subsequent testing.
The club are not involved in La Liga's opening fixtures this weekend and are due to start their season against Granada on 27 September.
Cases of coronavirus are rising in Spain with 12,183 positive tests being recorded in the last 24 hours, along with 48 deaths.
Partey's side will begin their 2020/21 LaLiga season at home to Granada on September 27.