Masvidal is down one cornerman at UFC 251 after his long-time American Top Team trainer has been diagnosed with the coronavirus.
Brown received his positive test on Monday in Las Vegas during pre-fight screenings required to travel to 'Fight Island'.
The 44-year-old won't travel to Abu Dhabi as Masvidal competes for a UFC title for the first time in his storied fighting career.
'Gamebred' will likely still have four cornermen for his fight against Usman.
According to ESPN, Paulino Hernandez, Jesus Gallo and Abraham Kawa will be in his corner and he's yet to make a decision on the fourth now that Brown is out.
Brown was in the corner for Dustin Poirier's 'Fight of the Year' contender against Dan Hooker at UFC Vegas 4.
But the "heartbroken" coach won't be in the corner for when Masvidal faces Usman on Saturday.
"Just heartbroken I'm not going to see Jorge win the world championship in person," he told Ariel Helwani.
"Nobody has paid more dues. Jorge is also one of the most thoughtful athletes I have ever met. He makes everyone feel they are with him and a huge part of this journey.
"The truth is this guy has been honing his skills for more than 20 years and developed one of the highest fight IQs ever seen in the sport.
"As far as being COVID positive, I feel good. The only pain I feel is in my heart."
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