Atletico Madrid duo Diego Costa and Santiago Arias have tested positive for COVID-19, the club have confirmed.
Both Costa and Arias underwent testing during their vacations and are in quarantine, with Atletico adding that both players are asymptomatic.
The rest of Atletico's squad – minus players currently on international duty – all returned negative results ahead of the start of pre-season.
However, with Costa and Arias in isolation, neither will take part in the start of pre-season training for Diego Simeone's side.
Former Chelsea striker Costa made 23 LaLiga appearances last season, scoring five goals.
Arias – who has been linked with a move away from Atletico in this transfer window – was restricted to just 14 league appearances as he played second fiddle behind Kieran Trippier.