Oleksandr Usyk is lobbying to face the winner of Anthony Joshua's rematch with Andy Ruiz Jr but Kubrat Pulev is also in the mix.
Joshua fights to regain the IBF, WBA and WBO heavyweight titles that he lost to Ruiz Jr in a December 7 meeting, live on Sky Sports Box Office, while two mandatory challengers lurk.
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Usyk (WBO) and Pulev (IBF) are both due an opportunity at the champion.
"The winner of Ruiz Jr vs Joshua will have to choose who they are going to fight," promoter Eddie Hearn told Sky Sports.
"We're going to have a problem where [Usyk and Pulev] both say: 'you've got to fight me next'."
About Usyk, Hearn said: "He really wants it."
The IBF had previously told Sky Sports that they expected their mandatory, Pulev, to receive the next shot at Ruiz Jr or Joshua.
"Ours has to come first. The organisations have agreed that the IBF mandatory would be next."
Ukraine's Usyk became the undisputed cruiserweight champion last year, then knocked out Tony Bellew.
His heavyweight debut against Carlos Takam was cancelled when Usyk suffered a bicep injury but a new opponent is set to be announced.
"He was going to fight Takam, now he'll fight another world ranked opponent," said Hearn. "He doesn't mind who he fights."
Usyk previously told Sky Sports that he hopes to challenge Joshua, not Ruiz Jr.
"Anthony Joshua at Wembley," answered Usyk when asked for his dream fight.
"I think it would be much harder for me to fight Joshua than Ruiz.
"If you want to be the best, you have to fight the best."
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