Atletico Madrid head coach Diego Simeone has tested positive for coronavirus, the LaLiga club have confirmed.
Atletico's full squad and coaching staff underwent COVID-19 tests on Friday after returning from their pre-season training camp in Los Angeles.
The latest round of testing was prompted by an unnamed member of the travelling party returning a positive on Thursday.
Simeone is now undertaking a period of isolation and is not displaying any symptoms.
"The analysis of these new samples in the laboratory has determined that our trainer, Diego Pablo Simeone, has given a positive result for COVID-19," Atletico said in a statement.
"Fortunately, our technician does not present any symptoms and is at his home isolated and fulfilling the corresponding quarantine after being concentrated with the team since last Monday."
Atletico are due to travel to Cadiz for a friendly on Tuesday before beginning their LaLiga campaign at home to Granada on September 27.
Simeone's side have been granted a later start to the domestic 2021-22 campaign due to their involvement in the latter stages of last season's Champions League, where they lost 2-1 to RB Leipzig in the quarter-finals.