Briton Kell Brook has cancelled his IBF world welterweight title clash with Diego Chaves on Saturday, 24 October after sustaining a rib injury in sparring.
Brook, 29, who was set to make the third defence of his title, was taken to hospital after suffering the injury on Thursday.
"Kell was desperate to fight but it was impossible," said promoter Eddie Hearn.
"We'll look to reschedule the bout for the end of the year."
Brook's fight was set to top the bill at the Sheffield Arena, but that honour will now go to the WBA interim world middleweight contest between Chris Eubank Jr and American Tony Jeter, with the Briton seeking to retain his title.
Another bout will see Doncaster's Gavin McDonnell aim to defend his European bantamweight belt against French former world title challenger Jeremy Parodi.