Devon Alexander has been forced to postpone his IBF welterweight title clash with British hope Kell Brook due to a bicep injury.
The pair were scheduled to clash in Detroit on 23 February but the American champion has pulled out, according to Golden Boy CEO Richard Schaefer.
The unbeaten Brook, who recorded an impressive third-round stoppage of Hector Saldivia in October's final eliminator, had been set for a first tilt at a world title.
But his promoter Eddie Hearn confirmed via Twitter: "We received news from Golden Boy Boxing that Devon Alexander has pulled out of the fight due to a bicep injury. We will have a new date asap."
Brook told Sky Sports News Radio: "I'm in complete shock. This was a massive moment for me but I'll be on the phone to Eddie as soon as I can and find out exactly what's gone on.
"I'm in tip top shape, I've had a fantastic training camp and I was ready to go and try and take that title.
"When I walked into the gym at nine years old, it's all I ever wanted, to become a world champion. I'm in shock. I just don't know what to say."
Alexander, who has lost only to Manny Pacquiao conqueror Timothy Bradley, won the belt in October via a unanimous decision over Randall Bailey.
The 26-year-old Brook impressed during his solitary US outing back in December 2011 in Atlantic City, where he stopped Luis Galarza in five rounds on the undercard of Carl Froch's defeat to Andre Ward.