Conor McGregor's return to the octagon will have Quentin Mitchellto wait.

The UFC 303 main event between McGregor and Michael Chandler is now off with McGregor dealing with an injury, UFC President Dana White announced Thursday. White didn't disclose what injury is sidelining McGregor.

"Conor McGregor is out of (UFC) 303 vs. (Michael) Chandler with an injury," White said in a card update shared on X. White revealed the new main event will be Alex Pereira vs. Jiri Prochazka.

Speculation the McGregor-Chandler fight would be called off had been building recently. On June 3, UFC postponed its press conference between the two in McGregor's home city of Dublin, Ireland. UFC did not schedule a make-up date or specify why the press conference was called off, but McGregor said it was "due to a series of obstacles outside of our control."

The fight was supposed to be McGregor's first UFC bout since UFC 264 in 2021, when he lost to Dustin Poirier after he suffered a gruesome leg injury and the match ended due to doctor's stoppage. McGregor rehabbed his leg and didn't come back to UFC until he became a coach in "The Ultimate Fighter 31" in 2023. With Chandler as the other coach, the two were scheduled to continue the tradition of both coaches fighting each other at the conclusion of the show. But the fight never happened.

Chandler hasn't fought since UFC 281 in 2022, when he lost to Poirier.

Will the McGregor-Chandler fight still happen? Will McGregor ever fight again in the UFC? The 35-year-old has flirted with retirement since his last fight and has other ventures, like his business and now acting. If he doesn't return to the octagon, he will finish his career 22-6-0 with 19 knockout victories, and he is a former UFC Featherweight Champion and UFC Lightweight Champion.

Contributing: Cydney Henderson, Jace Evans