Heavyweight star Anthony Joshua has exercised his contractual rematch clause with Oleksandr Usyk for the unified heavyweight championship after losing to Usyk in September, per ESPN's Mike Coppinger.

"Back in the game and looking for him to become a three-time world champion," Joshua's promoter Eddie Hearn said Saturday.

The 34-year-old Usyk (19-0, 13 KOs) dominated the first fight, winning a unanimous decision on Sept. 25. It was the 31-year-old Joshua's second loss in his last four fights, as he also lost to Andy Ruiz Jr. by TKO in June 2019 (though he won the rematch in December of that year). 

For his career, Joshua is 24-2. He'll obviously be keen to go 2-0 in his rematch bouts. 

For now, a Joshua vs. Tyson Fury matchup remains on hold. Fury is finishing up his trilogy with Deontay Wilder on Saturday night, and Coppinger noted that the WBC "ruled that if the winner of Saturday's bout doesn't unify with Usyk next, that the victor will be ordered to fight Dillian Whyte, the long-standing WBC No. 1 contender."

A Joshua-Fury fight feels inevitable, but the timing remains in flux, depending on how other chips fall in the heavyweight division.

One thing is for certain—if Joshua was overlooking Usyk with a Fury fight in mind when they first fought, he won't make that same mistake twice. 

"I've watched the fight, analyzed my preparations and identified my mistakes," Joshua told reporters after the loss. "I've learned my lesson. Don't worry about me. My spirit is strong!"