Andy Ruiz Jr believes that putting on too much weight due to "partying" contributed to his defeat to Anthony Joshua.
Ruiz Jr conceded the IBF, WBA and WBO heavyweight titles back to Joshua six months after shockingly beating him, and put on over a stone between fights. He weighed in at 20st 3lbs, three stone more than Joshua.
"I don't want to say that three months of partying affected me but, to tell the truth, it did," Ruiz Jr said after losing a unanimous decision.
"Being overweight held me back because I was looking for one or two punches, normally I go for three or four punches. It got the best of me.
"Being overweight, I couldn't perform to my best.
"I wasn't fluid, I couldn't move the way that I wanted to move.
"I should have trained harder, I should have listened to my coaches more.
"Maybe I shouldn't have put on all of this weight, I would have been faster and thrown more. I hurt him but let him survive.
"There's no excuse besides me not training hard, and putting on all this weight.
"I know what I didn't do, and what I should have done. I will learn from my mistakes.
"I weighed in too heavy and I wasn't able to throw my combinations."
Ruiz Jr apologised to his father and his trainer Manny Robles, and reiterated his desire for a third fight with Joshua.
"I would prepare a lot more. Being champion for the first time was hard," he said.
"[I would] train harder, and take it more serious. There is a lot of responsibility being the heavyweight champion of the world. The partying got the best of me.
"Being at 100 per cent, I can dominate anybody. We will work harder in the gym, prepare better and I will dedicate myself a lot more."