Undefeated bantamweight Umar was set to face Sergei Morozov on the preliminary card on Yas Island, Abu Dhabi, on Oct. 24, but news agency TASS announced via a team source that the fighter has been forced to withdraw from the fight.

"Umar Nurmagomedov was hospitalized in a hospital in Dubai with severe flu, fever and vomiting," the source told TASS.

RT Sport understands that Morozov's management has been informed that the fight with Nurmagomedov is now off, and that the UFC is seeking a replacement to keep the Kazakhstani fighter on the card.

Morozov was all set to make his UFC debut at UFC 254 against Nurmagomedov in a fascinating clash between undefeated Russian prospect and the Kazakh M-1 Global bantamweight champion.

But that matchup will have to wait for another day, with Nurmagomedov concentrating on shaking his symptoms and returning to full health.

The situation also raises concerns over the status of Umar's cousin and UFC lightweight champion Khabib, who is set to defend his title against Justin Gaethje in the main event at UFC 254.

Khabib and Umar were part of the same team preparing for their respective fights in their Dubai training camp, and the team, and the UFC will be hoping Khabib doesn't suffer the same health issues that have befallen his teammate and ruled him out of the event.