GGG-Canelo undercard to feature Jaime Munguia, David Lemieux, Roman Gonzalez

Unified middleweight world champion Gennady Golovkin and Canelo Alvarez are the stars of the show for their much-anticipated rematch, but they'll have a strong supporting cast on the undercard of their Sept. 15 fight at the T-Mobile Arena in Las Vegas.

Junior middleweight world titlist Jaime Munguia, former middleweight world titleholder David Lemieux and former pound-for-pound king and four-division world champion Roman "Chocolatito" Gonzalez will all be in action on the HBO PPV telecast (8 p.m. ET), Golden Boy Promotions announced Monday.

"This historic rematch between Canelo Alvarez and Gennady Golovkin can only be supported by an equally great undercard," Golden Boy CEO Oscar De La Hoya said. "That's why some of the best champions and contenders from all over the world will be featured on this event of international proportions, while some of our brightest prospects will have the opportunity of a lifetime on this undercard so they can one day headline events of this magnitude."

Mexico's Munguia (30-0, 25 KOs) -- the big-hitting 21-year-old and a breakout star since bursting on the scene with a crushing fourth-round knockout of Sadam Ali to win the title in May followed by an action-packed decision win over former titlist Liam Smith in his first defense July 21 -- will make his second defense against Brandon Cook in the co-feature.

"I'm very motivated to be in such an important card," Munguia said. "It will be the most important boxing event of the year. For me it is an honor to be on this card supporting Canelo Alvarez, who is also Mexican, on a date [Mexican Independence Day weekend] that is so special for Mexico, for me and for all of the people. We will do our best to please the public. I promise to not disappoint."

Cook (20-1, 13 KOs), 32, of Toronto, was supposed to face former welterweight world titlist Kell Brook in a junior middleweight fight July 28 in London on the Dillian Whyte-Joseph Parker undercard, but the bout was canceled because of a Brook injury. Now Cook is getting the unexpected title opportunity.

"It's always been a dream for me to fight for a world title. To be on the biggest fight card of the year with two of my favorite fighters is a dream come true," Cook said. "Jaime Munguia is an exciting, young, up-and-coming fighter. He has great punching power in both hands. I'm going to do everything possible to bring that world title back home to Canada. I can't thank Golden Boy Promotions enough for giving me this opportunity. I have a great team behind me and we will be ready Sept. 15. I'm coming to fight."

Cook has won two fights in a row since suffering his only defeat, a ninth-round knockout to unbeaten up-and-comer Kanat Islam last September.

Lemieux (39-4, 33 KOs), 29, of Montreal, lost his middleweight world title to Golovkin in a 2015 unification fight and is 5-1 since. Two fights ago, in December, he was at home as the mandatory challenger for world titlist Billy Joe Saunders but lost a near-shutout decision in a woeful performance he hopes to make up for when he faces Gary "Spike" O'Sullivan (28-2, 20 KOs), 34, of Ireland, in a fight that figures to be an action-packed given their come-forward styles.

Lemieux and O'Sullivan have been battling each other on social media for weeks in anticipation of their 12-round fight being finalized.

"I'm looking forward to fighting Spike O'Sullivan next. I have some unfinished business at 160 [pounds]," Lemieux said. "Spike is an action fighter, like me. He's a tough cookie and comes to fight. This is a fight for the fans. Come Sept. 15, I want to steal the show."

O'Sullivan, who turned down a chance to challenge Golovkin on May 5 in a fight he had begged for, hopes a win over Lemieux will position him for that eventual world title fight against the main-event winner.

"This fight is just another step towards fulfilling my ambition of becoming a world champion and providing a good life for my family," he said. "David Lemieux is just an object in my way that I fully intend smashing through. Then, I want Canelo or GGG -- either one, it doesn't matter. I'm going to war!"

Gonzalez (46-2, 38 KOs), 31, a likely future Hall of Famer and a legend in his home country of Nicaragua, will end a one-year layoff when he faces former strawweight world champion Moises Fuentes (25-5-1, 14 KOs), 30, of Mexico, in a 10-rounder that will open the pay-per-view telecast.

Gonzalez will try to shake off a two-fight losing streak to Srisaket Sor Rungvisai. Gonzalez lost his junior bantamweight world title to him to him by controversial majority decision in a March 2017 fight of the year contender on the Golovkin-Daniel Jacobs HBO PPV card, then suffered a brutal fourth-round knockout loss to him in the rematch last September.

"This will be my second fight in Las Vegas, and I look forward to fighting on this great show," Gonzalez said. "I have been training hard in California and will give a good show for the fans. I respect Moises Fuentes, and he will be a strong challenge for me."

Fuentes is 1-3 in his past four fights and in need of a victory as much as Gonzalez. Fuentes is coming off a first-round knockout loss in a flyweight world title fight to Daigo Higa in February.

"This will be a difficult fight because of Gonzalez's style of fighting, but it won't be impossible," Fuentes said. "In boxing, nothing is written. I still have what it takes to do it -- a good record and a lot of potential. I'm confident I will win this fight and Gonzalez will be a big trampoline for me to join the highest levels of boxing."

The untelevised portion of the card will include junior welterweight knockout artist Vergil Ortiz Jr. (10-0, 10 KOs), 20, of Dallas, Texas, one of boxing's top prospects, against Roberto Ortiz (35-2-2, 26 KOs), 32, of Mexico, in a scheduled 10-round bout.

In other untelevised bouts, welterweight prospect Alexis Rocha (11-0, 8 KOs), 21, a southpaw from Santa Ana, California, will face Carlos Ortiz (11-2, 11 KOs), 33, of Mexico, in an eight-rounder; featherweight Francisco Esparza (8-0-1, 3 KOs), 23, of Las Vegas, will fight an opponent to be announced in a four- or six-round bout.