UFC 313 has lost two fights just hours before the start of the event because of illnesses.

Curtis Blaydes withdrew from his heavyweight bout against Rizvan Kuniev and John Castaneda was forced out of his featherweight tilt with Chris Gutierrez, the promotion announced Saturday afternoon.

As a result, Saturday's event at T-Mobile Arena in Las Vegas will proceed with 10 fights, including the main event between light heavyweight champion Alex Pereira and Magomed Ankalaev.

Blaydes said on social media he contracted norovirus Friday night.

"Worked through the night to try and recover but my body wouldn't cooperate," Blaydes wrote on his Facebook page. "Fight going to be booked for a later date. Apologize to (the) fans and my opponent, (but) we will have this fight very soon."

Blaydes-Kuniev was scheduled to serve as UFC 313's featured preliminary bout. Blaydes, the No. 5-ranked heavyweight, was looking to rebound from a knockout loss to interim champ Tom Aspinall in July. Kuniev, meanwhile, was slated to make his Octagon debut after earning a contract on Dana White's Contender Series last year.