Manny Pacquiao has lost his WBO welterweight belt to Timothy Bradley after a controversial split decision victory for the challenger at Las Vegas' MGM Grand.
Pacquiao appeared to have done more than enough to take the decision, despite slowing down in the later stages, but was left stunned as two judges scored the bout 115-113 to the unbeaten Bradley and one handed the win to Pacquiao by the same score.
Defeat must now place the long-delayed but much-debated super-fight between Pacquiao and Floyd Mayweather Jr in serious doubt.
The win improves Bradley's record to 29-0, with 12 knockouts, but there is sure to be considerable discussion about the manner of this result.
Pacquiao's entrance to the fight was delayed, with the Filipino reportedly using a treadmill working on tight calves.
When he did arrive, he started sluggishly in the opening round only to land three meaty lefts in the closing moments to apparently edge it.
Bradley was allowing too many lefts to land, but was working hard to keep himself in the game, landing decent right-hands in the second and third round.
Pacquiao nevertheless looked comfortable, boxing within himself but seemingly controlling the pace.
By the fifth round Bradley was in visible discomfort with an injured foot.
A pattern had started to emerge, with Bradley attempting to come out hard at the start of each round but Pacquiao finishing strongly and connecting with some considerable blows.
Bradley enjoyed his best moments of the fight in the last three rounds as Pacquiao's control waned a little and the challenger unleashed an array of punches in the 12th to close on a high.
When the judges returned their verdicts the crowd reacted angrily and began to jeer, while Pacquiao looked incredulous.