Devon Alexander was ahead of Juan Urango by only one point on two of the judges' scorecards going into the eighth round of their light welterweight title unification bout.
The closely contested fight seemed headed for 12 rounds - until Alexander landed one powerful right uppercut.
Alexander floored Urango with that thunderous punch and then knocked him out with another uppercut at 1:12 of the eighth round to unify the WBC and IBF light welterweight titles on Saturday night at the Mohegan Sun Arena.
``I knew it would be the magic shot and it was,'' Alexander's trainer, Kevin Cunningham, said of the uppercut that started his fighter on the way to victory.
Alexander (20-0, 13 knockouts) made a successful defense of his WBC title, while taking away the IBF title from Urango.
Urango (22-3-1) had won the sixth round on all three judges' cards and carried the action in the seventh. But Alexander abruptly turned the fight around in the eighth.
``Our whole training camp we practiced that right uppercut,'' Alexander said.
Urango, a Colombian who now fights out of Cooper City, Fla., got up quickly after that first uppercut, but appeared dazed. Alexander pounced with the right cross that wobbled Urango, and then followed up with the uppercut that finished the job.
``I'm ready for anybody now,'' Alexander. ``I'll take on Zab Judah or Tim Bradley, whoever they put in front of me.''
Alexander, a southpaw from St. Louis, controlled the action in Round 1 with his jab, though he did take one good, hard right. Urango continued to stalk Alexander in Round 2, landing the occasional hook, but just as the bell sounded to end the round, Urango was blasted with a right to the head.
After an uneventful Round 3, things heated up in Round 4. Both fighters landed solid blows. A counter right hand by Urango caught Alexander flush the face, but it failed to slow him down.
Urango continued to be the aggressor in the fifth round, rattling Alexander with an uppercut midway through the round. Urango kept the pressure on in Round 6, and seemed to be frustrating Alexander with his relentless attack.
It was more of the same in the seventh. Urango landed the harder shots. Alexander scored with his jab. The momentum appeared to be clearly with Urango, whom the crowd began to get behind, sensing that an upset was likely.
Alexander dashed those hopes quickly.
``I don't know why the crowd was getting excited, I wasn't hurt by any of his punches,'' Alexander said. ``I was surprised by that. And I began to move around a little more to avoid those shots. Speed kills. I had too much speed for him.''
It was Alexander's first fight since August 2009 when he faced Junior Witter, who retired before the start of Round 8 because of a left hand injury. Alexander was comfortably ahead on all cards when the bout was stopped.
Urango's two previous losses came to fighters who were also unbeaten when he faced them.
Ricky Hatton was 41-0 when he handed Urango his first loss in January 2007 in an IBF light welterweight title bout.
Andre Berto was 24-0 when he defeated Urango in May 2009 for the WBC welterweight title. Urango lost decisive unanimous decisions in both bouts.
