Eddie Hearn, promoter of Matchroom Boxing, revealed that he has tested positive for COVID-19 and will have to leave the bubble ahead of Sunday's card in England headlined Joshua Buatsi squaring off against Marko Calic.  

"Gutted to just find out I tested positive for Covid-19 today and have to leave the bubble immediately," Hearn posted on Twitter. "Thankfully, all other tests were negative. Heading home to rest - catch up tomorrow."

All 12 fighters who are scheduled to be on the card, which takes place from Marshall Arena at Stadium MK in Milton Keynes, England, tested negative. Since Hearn left the bubble, he cannot be at any of the remaining fight week activities unless the test was a false positive. 

This is Matchroom's second round of "Fight Camp," highlighted by Alexander Povetkin rebounding from two knockdowns to knock out Dillian Whyte on Aug. 22. 

After the show on Sunday, one of the upcoming notable cards occurs in Mexico on Oct. 23, led by Juan Francisco Estrada defending the WBC super flyweight belt in a rematch against Carlos Cuadras; Román "Chocolatito" González puts the WBA super flyweight championship on the line vs. Israel Gonzalez; and Julio Cesar Martinez defends the WBC flyweight strap against Maximino Flores.