For Leo Santa Cruz, heavy is the head that wears the WBA featherweight crown

Leo Santa Cruz was adorned with a cherished title last year after he defended his featherweight belt with a second victory over crosstown rival Abner Mares at Staples Center: The King of L.A.

As he prepares for a title defense against against Tijuana’s Rafael Rivera at L.A. Live’s Microsoft Theater on Saturday, Santa Cruz has come to realize the heavy weight that accompanies the crown in his ongoing reign as World Boxing Assn. champion. In a striking disparity, Rivera’s guaranteed purse is $20,000 compared to Santa Cruz’s $1 million guarantee.

From the perch of a wheelchair that was frequently positioned next to the ring apron during camp at their City of Industry gym, Santa Cruz’s father and trainer, Jose Santa Cruz, continues his painful battle against the effects of myeloma spinal cancer.

“I’m doing what I can to keep him alive,” Leo Santa Cruz said in an interview last week at his Corona home. “If I had to go to hell to keep him alive, I will go.”

The boxer elaborated to reporters at his news conference Thursday, “It’s been really tough seeing my dad, seeing him struggling, his body breaking down … I feel depressed, sad.

“At the same time, he motivates me to go to the gym, to train hard, to get victories. I know when he sees me winning and working hard, that motivates him to continue fighting to beat cancer. He loves boxing. Boxing is his life. He’s told me to do a great fight, to continue growing my name and be the best in the division.”

Jose Santa Cruz, first diagnosed with cancer in 2016, said he endures a nightly routine of ingesting medication, including morphine, to tolerate the discomfort.

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The trainer said the daily pleasure he finds in driving to the gym in the Corvette that his son bought him is multiplied by the maximum effort his son has shown while preparing for the bout.

“I’ve been operated [on] three times from my back and my whole body” is in pain … my feet feel like they’re on fire,” Jose Santa Cruz said. “They’re burning, and sometimes I feel like my body’s just burning too much. It’s too powerful.”

But he adds, “I would rather die [near] the ring than at home.”

Leo Santa Cruz (35-1-1, 19 knockouts), a three-division world champion, is participating in his seventh consecutive featherweight title bout.

The fact that two of those victories have come over Mares has affected this camp after the former three-division champion from Hawaiian Gardens withdrew last month from his Feb. 9 super-featherweight title fight against Gervonta Davis because of a detached eye retina that threatens to end his career.

“I feel for Abner and never wanted anything like that to happen to him. He brought out the best in me,” Santa Cruz said.

Santa Cruz, 30, was supposed to fight Mexico’s Miguel Flores on Saturday, but Flores withdrew after a training-camp injury, which inspired the 24-year-old Rivera (26-2-2, 17 KOs) to pounce.

“I’m prepared. I’ve been training hard. I feel I’ll give everyone a good fight,” said Rivera, who knocked out Jose Ramos on Oct. 19 following back-to-back losses to former featherweight title challenger Joseph Diaz Jr. and Golden Boy Promotions prospect Joet Gonzalez.

“Tijuana’s always been known for sending in fighters who come out of nowhere, and Jaime Munguia has been the latest example,” Rivera said, referring to the 154-pound world champion. “I feel if he can do it, I can. And this is one of those great opportunities you have to take advantage of. This is what I want, what I’ve fought for. I want what he has.”

Santa Cruz, meanwhile, aims to position himself for a title unification later this year against World Boxing Council featherweight champion Gary Russell Jr. or a trilogy fight against former champion Carl Frampton. If neither happens, he said, he’ll consider moving to super-featherweight.

Ultimately, Santa Cruz said, the bout’s outcome is centered on uplifting his ailing father, who during this camp has proudly worn a hat reading, “Team Santa Cruz: The King of L.A.”

“When we were growing up, we had cars that cost around $500, and my dad used to tell people, ‘I’m going to have a kid who can be a world champion and we’re going to have nice cars,’” Leo Santa Cruz said.

“And people used to say, ‘Poor guy, he’s crazy.’”

BOXING

Main Event: Leo Santa Cruz (35-1-1, 19 KOs) vs. Rafael Rivera (26-2-2, 17 KOs) for Santa Cruz’s WBA featherweight belt

When: Saturday

Where: Microsoft Theater, L.A. Live

Television: Channel 11; televised portion begins at 5 p.m.

Undercard: John Molina (30-7, 24 KOs) vs. Omar Figueroa Jr. (27-0-1, 19 KOs), welterweights; Donnie Marshall (10-0, six KOs) vs. Sebastian Fundora (11-0, seven KOs), super-welterweights

lance.pugmire@latimes.com

Twitter: @latimespugmire