Gilbert Burns, his brother Herbert (who just fought), and trainer Greg Jones have all tested positive for Coronavirus.
They were stopped from getting on the plane in Las Vegas and thus the fight against Usman at UFC 251 is scrapped.
It seems both Masvidal and Colby said they would do it but this was just probably words as the UFC was not going to pay either what they wanted.
The headliner will now be Alexander versus Max.