Conor McGregor's return to the UFC cage might have to wait until 2024.

Yahoo Sports' Kevin Iole reported the former featherweight and lightweight champion didn't officially register with the U.S. Anti-Doping Agency.

"UFC fighters must be in USADA's testing pool for six months before they're able to compete again, meaning sometime in January 2024 is now the earliest McGregor could fight Michael Chandler, whom he's appeared with on the reality series, The Ultimate Fighter," Iole explained.

Iole also raised doubts over how soon into 2024 McGregor might be prepared to fight. His fiancée, Dee Devlin, is pregnant, which will occupy much of his focus. He may not want to go full bore into training during the holiday season, either.

Fans naturally got excited about McGregor's involvement in The Ultimate Fighter with the hope it presaged a future encounter with Chandler. UFC president Dana White said in May he was "hopeful" it would come together this year.

That's obviously out the window now. Chandler called his TUF rival out on social media once reality set in.

McGregor hasn't fought since July 2021, when he suffered a broken leg in the first round against Dustin Poirier. That was his third loss in four bouts, putting a dent into the aura he had built for himself as he rose to the top of the promotion.

Still, the 34-year-old remains one of the biggest names signed to UFC, and if Jon Jones' comeback is any indication, his drawing power is unaffected by his lengthy layoff.

Jones beat Ciryl Gane in the main event of UFC 285 in March, his first fight in a little over three years. Endeavor CFO Jason Lublin said on a May investor call UFC 285 was the "highest-grossing commercial pay-per-view event within the past 12 months."

A similar windfall would almost certainly follow McGregor's long-awaited comeback.

Of course, this is all predicated on him wanting to actually fight again, and there may be no guarantees on that front when the situation has already dragged on for this long.