Lightweights Marquez, Diaz face heavy burden in rematch

Their first meeting, 17 months ago, was voted fight of the year. Given the developments since then, Saturday’s rematch between champion Juan Manuel Marquez and Juan Diaz could well prove to be the last big fight of his career for the loser, who risks banishment to boxing’s second tier.

Marquez (50-5-1, 37 knockouts) will turn 37 next month. He’s coming off a one-sided, unanimous-decision loss to Floyd Mayweather Jr. 10 months ago, and now has to repeat the breathtaking resiliency he displayed in the 2009 bout against the younger Diaz, withstanding his opponent’s best early-round shots before claiming a ninth-round knockout.

Diaz (35-3, 17 knockouts) is 10 years younger, but he’s also seeking a comeback victory, having lost three of his last five marquee bouts, with one of his victories highly disputed. Las Vegas oddsmakers say Diaz is nearly a 4-1 underdog to Marquez in this 135-pound World Boxing Assn./World Boxing Organization lightweight championship bout at Mandalay Bay Events Center in Las Vegas.

Marquez will earn $1 million for the fight and Diaz will get a guaranteed purse of $540,000, the Nevada State Athletic Commission reported Friday.

“This fight, I’m ready, and I wasn’t ready before for all those lights and glamour,” Diaz said. “I’m not going to fight like an amateur.”

Officials at Golden Boy Promotions, which signed Diaz two years ago with hopes of bringing aboard the sport’s next great star in the “Baby Bull,” are now portraying the Texas fighter’s standing in stark terms.

“It’s do or die,” said Golden Boy President Oscar De La Hoya. “Juan Diaz has to look sharp in this fight, make adjustments from the first fight. We know he comes forward and fights. Can he do anything else? Those are the tough questions people are asking.”

Golden Boy matchmaker Eric Gomez said Diaz “has become one-dimensional. He can overwhelm guys by coming at you, but … the great counter-puncher Marquez exploited that. The reason why he was so successful is also part of his demise now.”

Diaz, after winning a controversial hometown decision over Paulie Malignaggi last August in Houston, was decisioned by Malignaggi in their December rematch in Illinois.

Diaz has veteran trainer Ronnie Shields on his side and maintains a new conditioning routine employing swimming, tire pushing, ladder climbs and monkey-bar lifting. All that has Diaz confident he can produce 12 aggression-filled rounds without fatigue zapping him as it did in the first Marquez bout.

“I have to be aggressive; I know aggression works,” Diaz said. “But I can’t give Juan an easy target. I’m going to get into my boxing stance and fight smart. I don’t think it’s do or die for me; I don’t believe my career’s on the line. I’m going to win the fight, and if I lose and the boxing public and promoters think it is over for me, I have so many other things going.”

Diaz is a graduate of the University of Houston, and in October he plans to take his law school admission exam, with an ambition one day to represent boxers and other athletes as a lawyer-agent.

Marquez, meanwhile, wants to avoid a second straight loss after the debacle of his September 2009 bout against Mayweather in what was supposed to be a 144-pound fight. However, Mayweather paid a fine for weighing in beyond the limit, then bloated up to a nearly laughable size advantage over Marquez, who fought at 130 pounds as recently as 2008.

“Mayweather didn’t respect the weight, but that’s behind me,” Mexico’s Marquez said through an interpreter after a recent workout. “I’m expecting to give a great fight. I’m conditioned and have prepared physically and mentally very well for this one. I definitely expect a continuation of the first fight. [Diaz] is fast; he’ll throw a lot of punches.

“But I’ve showed I don’t get tired. I went 12 rounds with Mayweather weighing 15 pounds more than me, and I’ve been through 24 rounds with [ Manny] Pacquiao [with a 2004 draw and 2008 split-decision loss]. I’ve showed I’m always willing to fight.”

After Pacquiao fights Antonio Margarito on Nov. 13, Marquez said, he will renew his call for a third bout against Pacquiao should he beat Diaz again. If Marquez can’t get the Pacquiao bout, De La Hoya expects Marquez to enter the talented 140-pound division with a possible date against WBA light-welterweight champion Amir Khan.

“The Mexican fan loves Marquez’s style, his determination,” De La Hoya said. “I don’t believe he’s lost anything.”

He has to hope not. There’s so much to lose — for both Marquez and Diaz.

lance.pugmire@latimes.com