Tommy Langford was beaten by Avtandil Khurtsidze with a fifth-round stoppage as the Georgian set up a bout against WBO world champion Billy Joe Saunders.
The fight was for the WBO middleweight interim title, with the winner becoming Saunders' mandatory challenger.
Langford had backed himself to go on and beat Saunders, but he was floored with a fierce left-hook by 37-year-old Khurtsidze at Leicester Arena.
Promoter Frank Warren said Saunders would fight Khurtsidze on 8 July.
He told BT Sport the bout would take place "probably in London".
Langford, 29, was undefeated in 18 contests and captured the British title in his last bout.
"Langford could have had a field day, you could see Khurtsidze was blowing hard but fair to play him," Saunders said on BT Sport.
"I will show you who he is when I fight him. If I can't beat him I might as well forget about the big fights."
In Liverpool, Martin Murray, 34, beat American Gabriel Rosado, 31, via a majority points decision at the Echo Arena.
The judges ruled the fight 114-114 119-109 116-112 in the Briton's favour. Afterwards, Rosado angrily remonstrated with the judges over their "crazy" scoring.
But Murray told Sky Sports: "I said all along I was a level above him and I proved that tonight.
"I thought I won it cleanly. I would give him three rounds max. He got completely schooled, it's as simple as that. He proved he's a tough fighter but I was a step ahead."
Earlier, Rocky Fielding won the vacant British super-middleweight title with a split decision over John Ryder, the judges ruling 116-113, 114-115, 115-114 in the 29-year-old's favour.
And Joe Cordina marked his professional debut with a fourth-round stoppage win over Jose Aguilar in Liverpool.
The 25-year-old, who won 2014 Commonwealth Games bronze for Wales, is now set to face Jay Carney on the Anthony Joshua v Wladimir Klitschko bill at Wembley on 29 April.