EDMONTON, Alberta -- Demetrious Johnson won't be breaking Anderson Silva's UFC title defense record this weekend after all.

In fact, he won't even get the opportunity to do so.

Ray Borg, Johnson's UFC 215 opponent, was forced to withdraw from the fight on Thursday evening due to illness, thus canceling Saturday night's main event, MMA Fighting has learned.

As a result, the Amanda Nunes vs. Valentina Shevchenko women's bantamweight title fight will serve as the new pay-per-view main event in Edmonton.

According to multiple sources, Borg has been battling an illness this week and was deemed unfit to fight by UFC doctors. His illness was unrelated to his weight cut, sources say.

“It wasn't weight related,” Borg’s nutritionist Dr. Michelle Ingels of Perfecting Athletes told MMA Fighting. “Ray has been getting progressively more sick each day this week and still wanted to fight so badly that he put on a game face and went to all of his fight week obligations.

“However, prior to beginning the bulk of his weight cut the UFC doctor examined Borg and concluded that he was too ill to fight this week and needed time to rest and get better.”

Earlier on Thursday, Borg told MMA Fighting he had eight more pounds to cut before Friday morning’s weigh-in.

“That’s amazing for me,” he said.

The current plan is to rebook the flyweight title fight as soon as possible, but nothing has been finalized at this time.

In April, Johnson successfully defended the flyweight title for the 10th time, which tied Anderson Silva's record. Coincidentally, the UFC wanted to book Johnson vs. TJ Dillashaw for the potential record-breaking 11th defense, but Johnson campaigned for Borg, the true flyweight, to be his next opponent.

In another strange twist, the Nunes-Shevchenko title fight was canceled just hours before UFC 213 in July due to a Nunes sinus issue, prompting UFC president Dana White to vow that he wouldn't put Nunes in the headlining act in her next fight.

UFC 215 will currently proceed with 11 fights.

UPDATE: The UFC released a statement regarding the cancellation and offered refunds later Thursday. The flyweight bout between Henry Cejudo and Wilson Reis will move up to the main card. The full statement is below: