A knee injury has opened the door for Daniel Cormier to step in and challenge Jon Jones for the UFC light heavyweight title.

Officials announced on Wednesday that Alexander Gustafsson had suffered an injury to his knee in training and will not make a planned UFC 178 main event title fight with Jones.

Cormier (15-0) moved down to light heavyweight after defeating the likes of Frank Mir and Roy Nelson at heavyweight. The former U.S. Olympic wrestler defeated Dan Henderson earlier this year, and was scheduled for knee surgery himself. That will be put on hold for his shot at “Bones.”

Cormier posted a picture of a direct message that Jones sent him on Twitter that read, “I hope you’re ready to come to daddy.” Cormier responded with, “I am. I’m gonna (expletive) you up,” but added that he couldn’t send his back.

Jones (20-1) initially pushed for Cormier to be his next opponent after defeating Glover Teixeira. Last year, Jones earned a decision victory over Gustafsson. He holds wins over Quinton “Rampage” Jackson, Rashad Evans, Vitor Belfort, Chael Sonnen and others.