Real Madrid carried out corona tests on Monday where it turned out that Mariano Diaz was infected with the virus. The attacker has been isolated in his home.
"The player is in perfect health and follows the restrictions on staying at home," Real Madrid wrote in a statement.
The news comes just days before Real Madrid will travel to the UK for the return in the Champions League quarter-final against Manchester City on 7 August.
Following the lifting of the national emergency in Spain, the spread of infection in the country has picked up speed again. Most of the regions have introduced rules on wearing mouth guards, in Madrid the decision was hammered through on Tuesday. Several areas have been closed for entry and exit and people are urged to stay at home to avoid the spread of infection.
The UK has introduced a 14-day mandatory quarantine for travelers from Spain, but according to British media, professional sports teams are not covered by the decision.
Manchester City won the first match in Madrid 2-1.