Welterweight Keith Thurman is primed for his chance "to headline a show like this against a former world champion," which he will do against Julio Diaz on April 26 at the StubHub Center in Carson, Calif.

"To headline a show like this against a former world champion is something I've wanted to do for a long time," said Thurman, a 25-year-old from Clearwater, Fla., "and that day is here."

Thurman-Diaz is the main event of a Showtime tripleheader supported by THE RING's number one-rated junior welterweight Lucas Matthysse opposite rugged lightweight puncher John Molina and WBC lightweight titleholder Omar Figueroa Jr. against former amateur nemesis Jerry Belmontes, Golden Boy Promotions CEO Richard Schaefer officially announced on Wednesday.

In his last fight, Thurman (22-0, 20 knockouts) scored knockdowns in the fifth and final rounds of a ninth-round technical stoppage victory over Jesus Soto Karass in December.

In his previous bout, last July, Thurman scored a 10th-round knockout of previously unbeaten Argentine Diego Chaves, whom he dropped once each in the ninth and final rounds.

"I respect Julio Diaz and I will not underestimate him," said Thurman, a boxer-puncher nicknamed "One Time." "He knows that this may be his last shot and I expect the best from him but I'll be the one leaving with the victory."

Although Diaz (40-9-1, 29 KOs) is 0-2-1 in his past three fights, those bouts were a draw and a unanimous decision loss against unbeaten current IBF beltholder Shawn Porter and a close decision setback to former titleholder Amir Khan.

In succession, Diaz drew with Porter in December 2012, floored Khan in the fourth round in April of last year and was outpointed in December by Porter, whose next bout was a unanimous decision that dethroned Devon Alexander in December.

A former lightweight titlist, Diaz has been training alongside WBO 147-pound beltholder Tim Bradley, who has a rematch with Manny Pacquiao on April 12.

"This is a big opportunity for me to face a fighter that is feared by many but not by me," said Diaz. "I have been in the ring with far more dangerous and experienced fighters in the past and everyone knows that I come to fight. My previous opponents, Amir Khan and Shawn Porter will tell you that."

Matthysse (34-2, 32 KOs) was last in the ring in September when he was dropped in the 11th round of a unanimous decision loss to unbeaten Garcia, the RING, WBA and WBC junior welterweight champion. Before falling to Garcia, Matthysse had built a 4-2 record (with four knockouts) against six current or former titleholders, having floored all of them.

Last May, Matthysse registered three knockdowns during a third round stoppage of IBF 140-pound beltholder Lamont Peterson in a non-title bout for his sixth straight knockout win.

"Molina is the kind of fighter I respect and always want to compete against," said Matthysse, a 31-year-old Argentine. "He shows up to fight and we're going to give the fans the kind of show they want to see. I don't think it will last long but it will be something to see while it does."

The 31-year-old Molina (27-3, 22 KOs) is 3-2 with three knockouts in his past five bouts, the first of which was a first-round stoppage loss to former titleholder Antonio DeMarco in September 2012. Molina split his next two bouts, stopping Dannie Williams in the fourth round in January of 2013 before falling by majority decision to Andrey Klimov last June.

Molina has knocked out his past two opponents, coming from behind to stop previously unbeaten Mickey Bey in the 10th round last July and knocking out Jorge Pimentel in the second round in November.

"I'm excited to showcase myself against someone that I consider to be one of the best fighters in the world at 140 pounds," said Molina. "I am very well prepared to come in on fight night and do what I do best and that is to be victorious."

The 24-year-old Figueroa (22-0-1, 17 KOs) won his belt against Nihito Arakawa, flooring the Japanese veteran twice during a unanimous decision in July. Figueroa had to pull out of a scheduled March 8 defense of his WBC 135-pound defense against Ricardo Alvarez due to a hand injury.

"I am especially excited about this fight because I have wanted to get payback against Belmontes for longer than a decade," said Figueroa.

"I fought him in the amateurs and he always beat me because I was always shorter than him. Now I am taller, stronger and bigger than him and I am looking to beat him the way he beat me in the amateurs."

Belmontes (19-3, 5 KOs) spoiled the U.S. debut of previously unbeaten Will Tomlinson of Australia on March 8 and is looking for similar results against fellow Texan Figueroa.

"I beat Omar five times in the amateurs but it was just that, the amateurs; we were young," said Belmontes, who is from Corpus Christi while Figueroa is from Weslaco. "We have taken different paths as professionals and finally, they cross and we meet again. On April 26, he'll be beaten by me for the sixth time."