Andy Ruiz Jr said three months of partying and a lack of proper training left him “overweight” for his world title rematch with Anthony Joshua.
Ruiz, 30, was comprehensively out-pointed in Saudi Arabia, six months after shocking the boxing world by stopping Joshua in New York.
The Mexican vowed he would be “a lot better” if he gets a third fight.
“I should have trained harder. I should have listened to my team and coaches,” he said.
“For this fight I was overweight. I didn’t move how I wanted to.”