The fight between Yu Haozong vs Alen Amedovski on the UFC264 prelim card has been cancelled.
The middleweight bout was due to kick off the early prelim card but has now been removed with the fight card reduced to 12 bouts.
A report from ESPN claimed a breach of Covid-19 protocols in Amedovski's camp was the reason behind the bout being pulled.
Conor McGregor will bid to avenge his January defeat by Dustin Poirier at the top of the bill in Las Vegas tonight.
The Irishman was stopped in the second round by Poirier in Abu Dhabi, seven years after he himself stopped his rival in the first session.
The winner of tonight's main event will be the first to challenge recently-crowned lightweight champion Charles Oliveira later this year.
Amedovski was coming into his fight with Haozong on the back of a two-fight losing streak since joining the UFC from Bellator.
And his opponent was in exactly the same position but will not now have the opportunity to improve his record at the T-Mobile Arena.
The UFC confirmed the bout had been removed from the card but did not provide further details.
The main event, meanwhile, is expected to attract one of the biggest pay-per-view crowds in the promotion's history.
President Dana White has predicted it could top two million buys which would rank it second behind McGregor's fourth-round submission defeat by Khabib Nurmagomedov in 2018.
The Irishman knows he must beat Poirier if he is to keep alive his hopes of becoming a two-time lightweight champion.
But he has struggled for momentum since losing to Nurmagomedov, fighting just twice in almost three years.
His only victory came against veteran Donald Cerrone who is now riding a six-fight losing streak.
And the 40-second KO did little to erase McGregor's ring rust which was in evidence when he was beaten by Poirier 12 months later.
But the Dubliner is confident he has corrected the mistakes he made that night in the desert - and vowed to leave no room for error.
“In 16 hours time this man is going to learn if you take a person’s kindness and take it as a weakness, you must pay," he said on Friday.
"Tomorrow night I'm going to make this man pay with his life and I mean it. You are dead in that Octagon tomorrow night!"
