Jon Jones out of UFC 295 heavyweight title clash with Stipe Miocic
The current UFC heavyweight champion was slated to defend his title against former king of the division at Madison Square Garden on November 11th.
Dana White revealed that Jones - who many regard as the greatest MMA fighter of all time - will be sidelined for eight months.
The UFC president said: "Jon Jones was training last night, got injured, he was wrestling and he tore the tendon that connects your pec to the bone, off the bone.
"He's out for eight months and going to need surgery."
The light-heavyweight title clash between Jiri Prochazka (31) and Alex Pereira (36) will replace the bout as the card's main event.
As a result, Briton Tom Aspinall (30) will face Sergei Pavlovich (31) for the interim heavyweight title at the same event.
Aspinall will become the first Englishman to fight for an interim heavyweight UFC title and is aiming to be just the country's third recognised title holder in the organisation's history.
Michael Bisping (44) at middleweight and Leon Edwards (32) at welterweight remain the only two Britons to have ever won a belt in UFC.