Anthony Joshua has revealed he could weigh under 17 stone after shedding the pounds for his fight against Andy Ruiz Jr on Saturday.
The former WBA, WBO and IBF heavyweight champion will look to win back the belts he lost in stunning fashion against Ruiz earlier this year when the pair do battle in Saudi Arabia.
Joshua weighed 17st 9lbs for the June fight in New York, where he was knocked down on four occasions before suffering his first career defeat in a result that shocked boxing.
The Briton will come in dramatically lighter for the rematch after a training camp inspired by the methods of Muhammad Ali, though he insists his punching power has actually improved.
Joshua (22-1) has not weighed in at under 17st for a fight since 2014.
"I may be less than 17 stone," the 30-year-old said to BBC Sport. "I'm punching loose and heavy - rhythm and flow.
"Before I was trying to bench press a house. I used my body to get where I needed but then I started realising the sweet science of the sport. I am punching like a horse kicking backwards right now.
"When Muhammad Ali was training, he said he would build a shack to train in. There are clues to success and you have to go back to what it takes to be a great heavyweight champion.
"We had to bring in hard, rough sparring partners. I brought in the toughest and roughest."
But Ruiz (33-1) engaged in mind games by turning up to Wednesday's press conference in a New York Knicks jersey and insisted he has no concerns over Joshua's power, despite being knocked down himself in the third round of their first fight.
"Not really," Ruiz, also 30, said of the threat of AJ's power. "I was the one who had the strength, the one backing him up. When I jabbed, I pushed him away.
"I know he lost weight and that he will try and box me around, so it's my job to prevent that.
"I have been doing this since I was six and it is finally paying off. There is no way I am going to let these belts go, I will die trying. It has been a rollercoaster and now that I made the dreams come true there is no way I will let these go."
The development with Joshua's weight drop has led Hasim Rahman, the former world champion who stunned Lennox Lewis before losing a rematch in 2001, to back Ruiz for victory.
"I am leaning at the moment to Ruiz by knockout," he said.
"I just think Joshua has lost weight. I didn't see him with much fat to lose. I feel he may have lost muscle and that can be detrimental.
"He could win a decision if he executes perfectly and uses his distance. But if Andy hits him, Andy will finish him."