ATLANTIC CITY, N.J. (AP) -- Lucas Matthysse stopped Lamont Peterson in the third round Saturday night at Boardwalk Hall in a matchup of junior-welterweight champions.
Although both own pieces of the 140-pound title, a dispute among the sanctioning bodies prompted the fighters to meet in a non-title fight that lived up to the hype.
"Now we all know who the best 140-pound fighter is," Matthysse said through an interpreter. "No one has dominated Peterson like that."
Matthysse (34-2, 32 KOs) had two knockdowns in the third round.
The Argentine fighter brought a roaring crowd to its feet when he sent Peterson (31-2-1, 16 KOs) to the canvas with a left hook that thudded against his jaw. Peterson, from Washington, D.C., toppled over when he first tried to get up, but barely managed to beat referee Steve Smoger's 10-count.
Matthysse charged toward Peterson and connected with another left hook that put him down again. Although Peterson got up, Smoger stopped it at 2:14.
Matthysse, the WBC interim champion, put himself in position for a big fight against WBC regular champion Danny Garcia of Philadelphia.
"We have a new Manny Pacquiao," Golden Boy Promotions CEO Richard Shaefer said. "He's from Argentina and his name is Lucas Matthysse. Words can't describe how good he is, how exciting he is, how hungry he is. You sit in your seat and you don't question if he's going to knock his opponent out. You only question when."
Matthysse nearly ended the fight in the second round when he connected with a left hook to Peterson's forehead that put him down for the first time in the bout.
Peterson slowly got to his feet in that one and held on for the rest of the round.
"I feel good," Peterson said. "I'm a little upset that I lost, but I feel good. I felt as though I could have kept going but he hit me with his good shots. But tonight I guess he was the better fighter."
In the co-feature, IBF welterweight champion Devon Alexander topped Lee Purdy at the end of the seventh round when referee David Fields stopped the fight on the advice of Purdy's corner.
Alexander (25-1, 14 KOs) was supposed to be making his first defense of his IBF welterweight title, but Purdy (20-4-1, 13 KOs) failed to make the 147-pound weight limit.
With the victory, Alexander put himself in position for a potential fight against another English fighter, former junior-welterweight champion Amir Khan. Alexander also would relish a chance to face Floyd Mayweather Jr., regardless of weight class.
"If Amir Khan wants it, he can have it," Alexander said. "If Floyd Mayweather wants it, he can have it. I just want to fight the best fights."