Undefeated Jarrett Hurd lost his IBF and WBA super welterweight world titles after a shocking defeat by Julian Williams in Virginia on Saturday.
Hurd suffered the first knockdown of his career and lost the fight by a unanimous decision.
The judges scored the bout 116-111 115-112 115-112 in favour of Williams, 29, whose record improves to 27-1-1.
"J-Rock was a better man tonight. I'll be back," 28-year-old Hurd told the crowd at Fairfax's EagleBank Arena.
"He put me down for the first time in my career and he came out with the victory," he added.
Hurd was cut around his right eye in the eighth round, but went the whole 12 rounds in a bid to retain his titles.
"I'm just so blessed," said Williams, who has won five fights since his sole defeat, a fifth-round knockout by Jermall Charlo in December 2016.
"I worked so hard," Williams added. "They told me I was done. They told me I had no chin. I just got basic.
"The boxing world should stop condemning fighters after they take a loss. It's boxing, things happen. Plenty of great fighters took losses."
Dogboe loses rematch to Navarrete
London-based Ghanaian Isaac Dogboe lost his WBO world super bantamweight rematch against Emanuel Navarrete in Tucson, Arizona.
The 24-year-old, who describes himself as "born in Ghana, made in Britain", suffered a technical knockout in the 12th round.
Dogboe's father and coach Paul threw in the towel after being handed a second loss following the pair's initial bout five months ago at Madison Square Garden.
"The fight was not over. It is not over until it actually is. Hats off to him. He did a great job being the champion," Dogboe said.
Berchelt retains super featherweight world title
Miguel Berchelt retained his WBC super featherweight world title, defeating fellow Mexican Francisco Vargas in a sixth-round stoppage at Convention Center arena in Tucson, Arizona.
Berchelt, 27, won by technical knockout and improved to 36-1 with 32 knockouts in a rematch of their 2017 fight.
"He gave me my first opportunity for a world title so it is only fair I give him a shot to win it back," Berchelt said. "But his corner did the right thing."
"My trainer did what he is supposed to do. He is here to protect me," 34-year-old Vargas said after trainer Joel Diaz threw in the towel.