Little known American Danny Garcia stopped WBA titleholder and heavy favorite Amir Khan in the fourth round on Saturday to stay undefeated and add another super lightweight belt to his WBC title.
Khan bruised Garcia early in the bout, opening a small cut above his eye, and appeared in control through the first two rounds.
But Garcia turned the fight around in the third round, repeatedly sending the British 2004 Olympic silver medalist to the canvas.
Khan got back to his feet after a Garcia left knocked him down for the first time but seemed hobbled by the shot.
Referee Kenny Bayless allowed the fight to continue and Khan was fortunate to last until the bell after struggling to absorb two more heavy shots from Garcia.
Khan appeared to be over his struggles at the start of the fourth but was down again after taking another heavy Garcia right and tripping on the rope.
Although Khan again got back to his feet and started to throw shots of his own, a glancing left from Garcia hit him on the right temple and put the Briton on the canvas for a third time.
Khan again got back up but Bayless had seen enough and called the fight at 2:28 of the round.
''We got a little complacent and he took advantage and he caught me,'' Khan said of Garcia's decisive left hook that sent him down for the first time. ''I was a little surprised the referee stopped it. I thought he was going to let us continue. My mind was clear and I thought my legs were okay but I respect the referee, the judges and the commission, maybe they made the right call.
''It wasn't my night,'' Khan added. ''I was coming in with my hands down and Danny took advantage of that. He countered very well against me.''
Garcia now has the WBA title to go along with his WBC belt. He improved his record to 24-0 with 15 knockouts while Khan fell to 26-3 with 18 KO's.
''I always knew I would win this fight,'' Garcia said. ''I needed a great fighter in front of me to show how great a fighter I am. Now everyone knows.''
Khan's trainer Freddie Roach praised his fighter's performance at the start of the bout.
''We were fighting a good fight and all of a sudden, one punch changed it and in boxing you never know. I guess I have to congratulate Mr (Angel) Garcia (Garcia's father and trainer) also,'' Roach said.
Khan's record is now 26-3 with 18 wins coming from early stoppages and two stoppage defeats. His camp was quick to request a rematch.
''Amir said he will be back and hopefully Danny Garcia will come to England and maybe fight us over there,'' Roach said on Khan's behalf after the fighter was taken to hospital for precautionary scans.
Although Garcia appeared open to the prospect immediately after the fight, his father cut him off.
''Why give him a rematch? For what? He (Khan) disrespected Danny when he took him as an opponent. He thought he was a pushover. We're not giving him a rematch,'' Angel Garcia said.
Khan was originally scheduled to face Lamont Peterson on May 19 in a rematch of their Dec. 10 bout in which Peterson took Khan's WBA and IBF titles in a 12-round split decision. Just days before the bout, however, Peterson tested positive for synthetic testosterone.
The fight was canceled and Peterson was stripped of his WBA title, which was later restored to Khan.
Garcia beat Erik Morales for the WBC title on March 24.
On the undercard, Fernando Guerrero beat Jose Medina by unanimous decision and Phil Lo Greco, J Leon Love, Daquan Arnett, Jamie Kavanagh and Abner Cotto also won their bouts.
