WBC heavyweight world champion Deontay Wilder (40-0, 39 KOs) is getting more pressure applied on him by promoter Barry Hearn, who is the founder of Matchroom Sport.
Barry's son, Eddie Hearn, is the promoter of IBF, WBA, IBO and WBO world heavyweight champion Anthony Joshua (21-0, 20 KOs).
Joshua is scheduled to defend his titles against WBA mandatory challenger Alexander Povetkin at Wembley Stadium on the 22nd of September.
There were negotiations to make Wilder vs. Joshua for the fall, but the two sides were never able to reach an agreement on the financial particulars.
There is a deal now on the table, which offers Wilder $15 million to face Joshua on April 13 at Wembley.
Wilder has rejected those terms - which Barry Hearn says is a big financial mistake.
He says if Wilder is really confident of winning the bout - then he should sign a contract to fight Joshua in April, because that deal would also give him a 50-50 split in the immediate rematch.
Wilder wanted something closer to a 50-50 deal for the first bout.
"Wilder has to ask: 'Do I really believe I can beat him?'" said Barry Hearn to BBC Sport.
Hearn, whose son Eddie promotes Joshua, added: "Wilder's making a few million dollars a fight.
"Sooner or later the penny will drop where he says: 'I've been offered $15m, so every other fight I take I'm losing $10m and I believe I can beat him. If I beat him, the rematch is at 50-50 for sharing $100m and if I beat him twice, I'm the biggest thing in American sport.'
"So does he roll the dice or negotiate over a few million dollars? Joshua has signed the contract, all Wilder has to do is add his signature and 13 April at Wembley is done."
Wilder's return date is unknown at the moment, but the contest is being positioned for the fall - likely with WBC mandatory challenger Dominic Breazeale.