Scott Quigg's hopes of becoming a two-division world champion were lost on the scales as he weighed in 2.8lbs over the featherweight limit ahead of his bout against Oscar Valdez.
Quigg was bidding to wrench the WBO featherweight crown away from his hard-hitting Mexican opponent at the StubHub Center in Carson, California, this weekend but came into Friday's weigh-in at 128.8lbs.
California rules prohibit a fighter who is more than 2lbs overweight from attempting to shed the excess mass and, while Saturday's fight will still go ahead, the title will be on the line for Valdez only.
Valdez, who has won all 23 of his professional contests, 19 inside the distance, weighed in at 125.8lbs. If he loses to his opponent from Bury then the belt will become vacant.
Former WBA super-bantamweight champion Quigg (34-1-2, 25KOs) was at a loss to explain why he missed the weight.
Speaking on-stage after the weigh-in, broadcast on promoters Top Rank's Periscope page, Quigg said: "I apologise, I'm a professional through and through and it's not acceptable, but this is something that I really didn't expect.
"I've done everything, I apologise to Oscar and his team, Top Rank and everybody here. I have tried and tried and it's just not budged, there's nothing more I can say until I look into why it's happened.
"I am so diligent, so precise and everything was on track and my body just seems to have frozen and won't let go of any more weight. But I've put the work in and I'm still going to get the victory."
Valdez was phlegmatic afterwards as he vowed to retain his strap.
He said: "It won't make a difference. I did my job in the gym, I proved it on the scale and the result's going to be the same: I'm going to come out victorious. I'll be ready for him."