Aberdeen won't discover the fate of their Europa League tie with Sporting CP until a day before they are due to play them.
The Dons travel to Portgual for the third qualifying round but 12 members of their playing squad and staff - including manager Ruben Amorim - have tested positive with COVID-19.
The club have gone to a training camp in the Algarve to isolate themselves after their weekend league game was postponed with Gil Vicente because of the outbreak.
And UEFA have now informed the club they will take a final decision on whether the game can go ahead only on the day of the match, with Aberdeen already in Portugal.
Sporting will now arrange two tests - one 48 hours and a later one 24 hours before the game - and the results will only be known on the day of the game.
They also have to get the go-ahead from Portugal's Director-General for Health and then UEFA for the match to go ahead, with reports in Portugal indicating that call will be the responsibility of the regional health delegate from Lisbon and the Tagus Valley.
The winners of the tie face Austrians LASK or Dunajska Streda from Slovakia at home in the play-offs for the Europa League group stages.
