Umar Nurmagomedov, the MMA-fighter-cousin of Khabib, has been rushed to hospital in Dubai.
The rising UFC star is understood to have a staph infection leading to a high fever.
Initial reports claimed he was suffering from ‘severe flu, fever and vomiting’.
Umar was set to make his UFC debut on the prelim cards of UFC 254 next weekend.
But his bout with Sergei Morozov has now been scrapped.
RT report Morozov’s team have been informed that Umar is unable to take part and the UFC are seeking a replacement.
Umar, a 12-0 undefeated bantamweight, will instead focus on his recovery.
Khabib updated fans on his Instragram, explaining that Umar has been holed up in a hotel for the last few days but his health deteriorated, forcing him to hospital.
The news will spark fears over the health of UFC lightweight champion Khabib.
The pair were part of the same training camp as they prepared for the huge Fight Island event on October 24.
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Khabib headlines UFC 254 when he puts his belt on the line against Justin Gaethje.
However, Khabib’s Insta post gives no indication he is suffering as he wished his cousin a swift recovery.
This is the third time Umar’s UFC debut has been delayed.
His first bout at UFC 249 in April was scrapped due to coronavirus and he pulled out of his second in July after the death of Khabib’s father and trainer Abdulmanap Nurmagomedov.