Jacare Souza is out of UFC 249 after testing positive for coronavirus ahead of his bout at the controversial event.
The UFC is the first high-profile sport on US soil to make a comeback, with Tony Ferguson's bout with Justin Gaethje headlining at the VyStar Veterans Memorial Arena in Jacksonville, Florida.
Souza was due to face fellow middleweight Uriah Hall on the preliminary card, but the fight will not be taking place as the Brazilian fighter and his two cornermen have tested positive for Covid-19.
In a statement, the mixed martial arts company said: "UFC's medical team examined Souza and his two cornermen and found them to be currently asymptomatic, or not exhibiting the common symptoms of Covid-19.
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"As per UFC's health and safety protocols, all three men have left the host hotel and will be self-isolating off premises, where UFC's medical team will monitor their conditions remotely and will provide assistance with any necessary treatment.
"From their arrival earlier in the week until their departure today, Souza and his cornermen followed UFC health and safety protocols, including practicing social distancing, wearing personnel protective equipment, and self-isolating whenever possible."
Opponent Hall took to Twitter to send his best wishes to Souza, posting: "Brother I know it sucks I'm sorry you have to go through this I am beyond devastated for the missed opportunity I wish you nothing but recovery for you and your family."
UFC 249 was supposed to take place in Brooklyn, New York on April 18, only for it to be scrapped due to the coronavirus crisis.
"There have been no other positive Covid-19 tests reported from the remaining athletes participating in UFC 249," UFC's statement continued.
"The response to this development is indicative of the effectiveness of the health and safety measures UFC has put in place for this event.
"Saturday's UFC 249 card, which airs live on pay-per-view and is headlined by a battle for the interim lightweight title between No. 1-ranked lightweight contender Tony Ferguson and No. 4-ranked Justin Gaethje will proceed as scheduled with 11 bouts."
Dana White has been criticised and scrutinised because of his desire to push through with UFC events, but the UFC president told CNN: "I believe we can pull this off and do it safe.
"I don't think you're going to see crowds back at live sports for a while.
"Listen, we have families, too. I have a family; I don't want to hurt my family. I don't want to die.
"This isn't just some crazy, this is a well thought-out plan. We've had very, very smart people, doctors and people that have been involved with the UFC for a very long time working on this thing non-stop since it started.
"We believe that we have this thing in a place where it can be as safe as it can possibly be."
The current arrangement is thought to be a stopgap solution as White is developing plans to hold a number of cards from June on a 'fight island' at an unknown location.
He added: "The island was a concept we came up with where we could get people in from anywhere in the world. It's basically for our international fights. We can bring people from whatever it might be, to this island, set up the infrastructure, where we can do the proper, you know, everything is clean, you know, the testing."