Junior achiever

Julio Cesar Chavez Jr. has been portrayed by his opponent as a spoiled son of privilege, a silver-spooner who rode the preferential treatment of name recognition to the world middleweight title.

Lost in that theory is the burden of living up to the reputation of his father, one of Mexico’s national heroes, bearing close witness to that icon’s steep fall into alcohol and drugs, and finding the fortitude to stand as his own man.

Saturday night, the 26-year-old Chavez (46-0-1, 32 knockouts) has his stiffest test as a fighter when he meets Argentina’s Sergio Martinez (49-2-2, 28 KOs) in a pay-per-view bout at Thomas & Mack Center in Las Vegas.

“When you’re compared every single day of your life to this great legend, especially when you choose this profession, people are going to say you’re not hungry,” Chavez said about his father, Julio Cesar Sr. “I’m very hungry.”

Comparisons are inevitable when your father is a former three-division world champion who lost only six times in 115 pro fights by always coming forward, attacking the opponent’s body and effectively turning every bout into a thrilling test of manhood.

However, it seemed almost insulting how Chavez Jr.’s promoter, Top Rank, coddled him earlier in his career, having him headline pay-per-views and cashing in on the dad’s legacy as if it were a Las Vegas hotel trotting out Frank Sinatra Jr. onstage.

Something happened during the novelty act, though, as Chavez Jr. confronted a crossroads moment that tested his love of the sport.

In November 2009, Top Rank put Chavez as the main undercard fighter to Manny Pacquiao-Miguel Cotto in Las Vegas. Chavez won unimpressively, but later the result was changed to a no-contest because he tested positive for a diuretic.

“I thought about it, ‘What am I doing here? Do I need to be serious about this? Do I really want this? How much do I want it?’ ” Chavez . said.

Around the same period, Chavez Sr. had fallen into the abyss of substance and alcohol abuse.

“It’s just a horrible experience to go through something like that,” Chavez Jr. said. “You don’t know what to think, you don’t know what to do. You get frustrated. It’s a very difficult moment, something like a torture. Every day, you see something in someone you love going down.

“All I kept thinking about was this guy’s going to die on me. I was getting used to the idea, that he was gone too far, that if I we didn’t do something ...”

Chavez Sr. got sick in the summer of 2010 in Tijuana, and his son pushed for more than hospitalization, convincing doctors a transfer to a rehabilitation center was necessary.

“He was against it,” Chavez said of his father. “But he did it.”

The father’s road back to health coincided with his son’s winning his most impressive fight at the time, a decision over John Duddy.

Having united with famed trainer Freddie Roach in Hollywood, Chavez won the vacant middleweight title a year later, beating Sebastian Zbik at Staples Center, after the World Boxing Council elevated Martinez to emeritus champion.

Chavez followed that with title defenses over veterans Peter Manfredo, Marco Rubio and southpaw Andy Lee, the latter a technical knockout in June that convinced all handlers a date against the left-handed Martinez could be made.

That support staff includes his father, who reacted heatedly when asked if his son still needs to display more heart in the ring.

“You haven’t seen his fights? Are you crazy?” Chavez Sr. said. “He’s got all my genes.

“This is the fight where he’ll finally get the prestige and recognition from all of you guys.”

That’s the prevailing sentiment. If Chavez can beat the slightly favored 2010 fighter of the year, he will have truly emerged from his father’s shadow.

“I don’t think about ... where I am in the shadow,” he said.

The reality is he’ll never escape it, and Chavez embraces the value of his father’s career -- witnessing the great fights, imitating his father’s fighting spirit in the ring and getting casual lessons such as how to trick a southpaw.

“I feel it when I’m in the ring -- that style, the schooling, everything I ever saw from him,” Chavez said. “I can’t help it. It’s in the genes, it just comes out. I don’t even think about it. I just do it, because that’s what’s in my brain for all these years.”

Roach’s fight plan against Martinez is unabashedly Chavez: “We’ll be right in his face.”

Victory happens, said Chavez Jr., “with intelligence, a lot of activity. We cannot let this guy think. We have to be on top of him all night long. Don’t give him an edge. Don’t let him think he’s doing something right. Demoralize him as much as you can, early and often.

“I just want the fans to ... come out of there thinking I’m one of the best fighters in the world. This fight puts me a step closer. That’s what I want, that’s what I hunger for, to be the best fighter in the world.”

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lance.pugmire@latimes.com

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Fight facts

Who: Julio Cesar Chavez Jr. (46-0-1, 32 KOs) vs. Sergio Martinez (49-2-2, 28 KOs)

Title: Chavez Jr.’s World Boxing Council middleweight belt

When: Saturday

TV/Time: HBO pay-per-view, broadcast begins at 6 p.m.

Where: Thomas & Mack Center, Las Vegas