ARLINGTON, Texas -- Humberto Soto, a reigning junior lightweight titleholder, moved up from 130 to 135 pounds to outslug and outbox former titleholder David Diaz to claim a vacant lightweight title via unanimous decision on Saturday night.
The fight was the co-feature on the Manny Pacquiao-Joshua Clottey undercard before an excited crowd of 50,994 Saturday night at Cowboys Stadium.
Soto (51-7-2, 32 KOs), 33, of Mexico, bookended the victory with knockdowns in the first and 12th rounds.
The fight started with a bang as they clashed heads in the opening round. Soto was shaken up and Diaz was cut, but later in the round, Soto knocked Diaz down with a counter left hand.
Soto fired combinations throughout the fight while the slower Diaz (35-3-1, 17 KOs), 33, of Chicago, tried to get out of the way and had little success landing anything meaningful in return.
Soto, who will likely vacate his 130-pound title, also scored a knockdown on a flurry in the final seconds of the fight to punctuate his victory.
Two judges had it 117-109 for Soto and the third had it 115-111 for Soto.
"I think Diaz being left-handed was a little more difficult than I thought it would be, but I was able to control the fight," Soto said. "I just couldn't hit him as hard as I wanted. He's a real tough guy."
Diaz was fighting for only the second time since losing his lightweight belt to Pacquiao via lopsided ninth-round knockout in June 2008. In his next fight, Diaz scored a majority decision against former titleholder Jesus Chavez in September 2009, a win that hardly should have qualified him to fight for that belt again.
"I'm very disappointed," Diaz said. "It wasn't supposed to be this way. In the last round, that was no knockdown. I missed the punch [and went down]."
Gomez makes Castillo quit
Welterweight Alfonso Gomez (22-4-2, 11 KOs), younger, quicker and fresher, beat Mexican countryman Jose Luis Castillo (60-10-1, 52 KOs) to the punch all night until he quit after the fifth round.
Castillo then announced his retirement.
"I want to apologize to the public and I am definitely announcing my retirement because I don't have it anymore," said Castillo, the former two-time lightweight champ whose 2005 10th-round knockout loss to Diego Corrales is considered perhaps the greatest fight in boxing history.
Castillo, 36 and years past his prime, couldn't get off as Gomez, who starred in the first season of "The Contender," peppered him nearly at will. Castillo's right eye began to swell in the third round and his nose was also bloody.
Gomez kept him on the outside and moved just enough to prevent Castillo from landing anything serious. When the fifth round was over, Castillo returned to his corner with a look of resignation before referee Kenny Bayless waived it off at the request of the corner.
"I just don't have it anymore," Castillo said. "This guy is hitting me with both hands and there was nothing I could do. I can't hit him back. It's frustrating."
Gomez, 29, won his fourth in a row following his fifth-round knockout loss to then-welterweight titlist Miguel Cotto in 2008 and put himself in position for a bigger fight.
"I practiced a lot with [prospect] Brandon Rios and he pushed me hard like we thought Castillo would try to do," Gomez said. "I respect Castillo a lot. He has given us all entertaining fights. We thought he would pressure us, but he couldn't because I was hitting him with good shots."
• Middleweight John Duddy (29-1, 18 KOs) took a split decision from Mexico's Michael Medina (23-2-2, 18 KOs) to set up a possible return to Cowboys Stadium.
Duddy, an Ireland native living in New York, and Medina, who was making his United States debut, mixed up throughout the fight but Duddy got the better of the exchanges, including landing numerous hard right hands.
Medina didn't help himself when he was warned multiple times for low blows before referee Robert Chapa docked him a point for the infraction in the eighth round.
Two judges had it 96-93 for Duddy and the third had it 96-93 for Medina.
Duddy won his third in a row since an upset loss to Billy Lyell 11 months ago.
Top Rank put Duddy on the card to expose him to the considerable Hispanic community because it has designs on matching him with Julio Cesar Chavez Jr. later this year. That's a fight Top Rank's Bob Arum and Cowboys owner Jerry Jones have discussed as a headliner for a future card at Cowboys Stadium.
Before that, Duddy will fight on Top Rank's June 5 card at Yankee Stadium with the fight against Chavez tentatively slated for the fall.
• Junior featherweight Roberto Marroquin (13-0, 10 KOs) showcased himself in front of his hometown fans as he blew out Samuel Sanchez (4-2-1, 0 KOs) for a knockout at 1:36 of the second round.
Marroquin, one of Top Rank's most important prospects, entered wearing Dallas Cowboys colors and exited after dropping Sanchez twice for the knockout. He knocked Sanchez down in the first round with a left and finished him in the second with a pair of overhand rights that badly buckled Sanchez before he fell to the canvas as referee Bayless called it off without a count.
• Featherweight Salvador Sanchez (19-3-2, 9 KOs), the nephew of the Hall of Famer and former featherweight champ with the same name, knocked out Jaime Villa (8-8-2, 3 KOs) using a heavy body attack in the sixth round.
Mexico's Sanchez, 24, dominated Villa and knocked him down in the fifth round. In the sixth round, Sanchez's withering body attack took its toll. He scored a knockdown and Villa barely beat the count. Moments later, another left to the body knocked him down to a knee for the full 10 count as the fight ended at 1 minute, 9 seconds.
• Junior featherweight Eden Sonsona (19-5, 6 KOs) of the Philippines dominated former junior flyweight titlist Mauricio Pastrana (35-13-2, 24 KOs) of Colombia en route to a brutal eighth-round knockout in the scheduled eight-rounder. Sonsona, who had dropped the smaller Pastrana earlier in the fight, sent him crashing to the canvas a minute or so into the eighth round. A shaky Pastrana survived but Sonsona connected with a flush left to the head and Pastrana fell almost in slow motion before smashing his head on the canvas as the fight was immediately called off at 1 minute, 33 seconds.
Dan Rafael is the boxing writer for ESPN.com.