Former UFC featherweight title challenger Brian Ortega pulled out of his Dec. 21 main-event fight against the "Korean Zombie" Chan Sung Jung at UFC Busan in South Korea due to an undisclosed injury, Ariel Helwani of ESPN reports.

Ortega is reportedly expected to be out of action for around two-to-three months.

The UFC is working to keep Jung on the card for what would be his first appearance in his home country since 2008, but a replacement has yet to be finalized, added Helwani.

The winner likely would've been first in line to be the next challenger for the 145-pound belt, which champion Max Holloway is set to defend against No. 1 contender Alexander Volkanovski at UFC 245 on Dec. 14.

Ortega (14-1) hasn't fought since his suffering his first career loss to Holloway at UFC 231 in December. He's been sidelined with hand, nose, and foot injuries.

Meanwhile, Jung (15-5) produced a 58-second TKO victory over Renato Carneiro in June to earn the bout against Ortega.

UFC Fight Night 165 is the promotion's final event of the year. Light heavyweight contenders Volkan Oezdemir and Aleksandar Rakic are slated to face off in the co-main event.