Eddie Hearn has been forced to self-isolate after confirming he has tested positive for coronavirus.
The 41-year-old left Matchroom Sport's secure bubble ahead of Joshua Buatsi's bout with Marko Calic.
Hearn tweeted: "Gutted to just find out I tested positive for Covid-19 today and have to leave the bubble immediately.
"Thankfully all other tests were negative. Heading home to rest - catch up tomorrow."
Buatsi will take on Kalic for the WBA international light heavyweight title on Sunday in Milton Keynes.
Hearn insisted he was the only person to test positive in the wider camp building up to the fight to be staged at Stadium MK’s Marshall Arena.
Hearn's positive test comes as Scottish Premier League side Kilmarnock announced three more players have tested positive for Covid-19.
Killie had earlier cancelled training as they awaited results from another round of tests after the first three positive test results emerged on Wednesday.
The fate of Friday’s Rugby Park clash now hinges on the advice of health officials.
A statement from the Scottish football authorities read: “The Joint Response Group has tonight been informed by Kilmarnock FC that three further players have tested positive for Covid-19.
“This means six players in total have now tested positive and will require to self-isolate as per Scottish Government guidelines.
“The SPFL is awaiting further information from Kilmarnock FC and Ayrshire and Arran Health Board’s Test and Protect team tomorrow morning (Friday) to determine the implications of the test results for tomorrow’s Premiership fixture against Motherwell.
“The league body will make further comment upon receipt of that information.”
