New Zealand-born UFC fighter Mark Hunt has gone from not being on the UFC 200 card to being the headline act with Jon Jones failing a drug test just days out from his light-heavyweight title fight with Daniel Cormier.
Jones and Cormier were set to headline the card with their title fight but, as a result of Jones testing positive to a banned substance, Hunt's fight with returning former heavyweight champ Brock Lesnar has the top spot.
UFC president Dana White broke the news at a media conference in Las Vegas.
White said the violation is related to a drugs test Jones had on June 16.
"This sucks," White said.
"I don't know what to say. It's unfortunate.
"Obviously, he's got the chance to prove himself innocent before being held guilty but, if it's true, obviously super, super disappointing."
This is the second time Jones has failed a drugs test, also testing positive to cocaine metabolites in December 2014 ahead of his UFC 182 fight with Cormier.
He claimed that positive test was the result of a wild night of partying.
Jones, who holds a career record of 22-1, also served a suspension in 2015 for his involvement in a hit-and-run accident.
He made his comeback just two months ago, defeating Ovince Saint Preux via unanimous decision.
UFC head of Athlete Health and Performance Jeff Novitzky released a statement explaining the process for Jones' potential doping violation.
"Because Jones was scheduled to compete against Daniel Cormier this (Sunday) in Las Vegas, there is insufficient time for a full review before the scheduled bout and therefore the fight has been removed from the fight card.
"As a result, the three-round heavyweight bout between Brock Lesnar and Mark Hunt will become the UFC 200 main event."