Sunday's Essendon-Melbourne match has been postponed after Bomber Conor McKenna tested positive for COVID-19.
AFL chief executive Gillon McLachlan confirmed the decision a short time ago to clubs and then in a media conference at the MCG.
McKenna returned from Ireland last month and self-isolated for two weeks as per national protocols.
He then returned to the Bombers for full training, was named to play his first game of 2020 on Sunday and was with teammates as recently as Friday morning.
Importantly, he did not train on Saturday morning.
All players are required to complete a COVID-19 test 24 hours out from each main training session and match.
The postponement forced a reshuffle to the other two games on Sunday.
Gold Coast and Adelaide's game will move from 1:05pm AEST to 3:05pm AEST, while Fremantle and Port Adelaide's game will move from 6:10pm AEST to 8.10pm AEST. Both will remain at Metricon Stadium.