LOS ANGELES -- It's OK to cry.

It is the first thing boxer Marlen Esparza would, if she somehow could go back in time, tell the 11-year-old version of herself who walked into Rudy Silva's Elite Boxing Gym in Houston to train.

Crying might have released a lot of the heartache Esparza has carried. Now Esparza, 27, is embarking on a pro career, feeling stronger -- and yet more vulnerable -- than ever. She's set to fight Rachel Sazoff in Indio, California, on Thursday, in a bout televised on ESPN2 and ESPN Deportes.

As a child, Esparza was laser-focused on boxing. She had a hero in mind to emulate -- Salvador Sanchez, a gifted Mexican fighter who died in a 1982 car accident.

"It was the first time I saw someone that I wanted to be like," Esparza said, explaining that she watched Sanchez fight in old boxing videos purchased by her father, David, a Mexican immigrant who loved the sport.

"No puedes," her father told her, repeatedly rejecting her entreaties.

Esparza eventually persuaded her father to let her box, and Silva agreed to train her under one condition.

"I'm going to train you like a boy," Esparza recalled Silva telling her in 2000.

Tears weren't welcome in the gym. Besides, at the start, boxing brought Esparza joy as she proved herself.

"I was one of those who didn't believe in women's boxing," David Esparza said. "In her first fight, she convinced me. She had character; she was very brave, very aggressive. I've supported her ever since then."

Boxer Marlen Esparza at a red-carpet event in England last year, showing off her Olympic rings tattoo that commemorates her London 2012 participation. Jules Annan/Barcroft Media Barcroft Media/Getty Images

Esparza was so focused, she didn't realize at first the backlash she engendered. Boys who lost sparring sessions against her sometimes quit. "I was too young, too naïve," Esparza said of those early days. "The struggle wasn't getting into the gym. I was just one of those kids who wanted it."

That desire and her talent led to success. As Esparza moved into her teenage years, she became more aware of resentment.

"A lot of dismissal, a lot of disrespect," she said. "I was [an] outcast all the time and I didn't realize it until I got older."

On the heels of winning her first national championship in 2005, becoming the youngest to do so at only 16, Esparza returned to whispers and mutterings from some people at her own gym.

"They said I was going to get pregnant and they didn't understand why I was doing [boxing]," Esparza said. "It took a toll on my soul and my spirit."

The drive to prove doubters and critics wrong was only partly satisfied at the 2012 London Olympics, where Esparza earned a bronze medal in the women's flyweight division (112 pounds). Before the Games, Esparza's long record of success had already generated considerable endorsements -- and envy among some fellow boxers.

Esparza was bewildered about anyone's dismissal of her ability and longevity. "I can fight," she said. "I'm not just a pretty face."

After 2012, Esparza moved on from Silva's coaching, training at times on her own. She found that anger can be useful as fuel.

"I won my first world championship, which is arguably harder than the Olympics, by myself," Esparza said of her 2014 title.

Esparza came up just short of qualifying for the 2016 Rio Games, losing to fellow Texan Virginia Fuchs in the final match at the trials last year. The crushing disappointment from that setback has propelled Esparza toward a pro career with more force.

"Marlen's generation is the first Olympic generation," David Esparza said, observing the general rise of women's boxing. "They've done well. People will start to get excited. It's going to be a main event one day, same as the men."

"Going pro was the thing for me," Marlen Esparza noted. "This is where I still get to show what I can do."

She's not particularly concentrated on Sazoff, 26, as an opponent. "I have no clue," Esparza admitted about Sazoff's strengths. "I'm going to be in there worrying about myself. I don't think I'm going to see anything I haven't seen before."

Esparza has boxed for most of her life, often participating in tournaments knowing little about upcoming rivals. "No matter what, I'm going to get the job done," she said. "She'll come and do what she has to do. But I was born for this."

Esparza has the prime example of her own promoter, boxing legend Oscar De La Hoya, to follow in the ring. "We feel she is someone who can revolutionize women's boxing in the U.S. and bring awareness and excitement," Golden Boy Promotions president Eric Gomez told ESPN's Dan Rafael in December, when Esparza became the first female boxer signed to the company.

Her father sees it happening already and his voice chokes slightly with pride as he explains in his native language how his daughter is opening doors for other females following her path: "Está abriendo puertas para las mujeres que van detrás de ella."

Though the Hispanic community traditionally supports its own in almost every sport, Esparza admitted to feeling bereft in that regard so far. "When it comes to [women's] boxing, in my experience, no," Esparza contended, but ultimately remained hopeful. "I think it'll change."

And Esparza wants to strengthen her ties to the Hispanic community. "I want to improve my Spanish," Esparza said, explaining she understands the language well, but gets anxious when speaking it publicly. "I want to communicate with my people more."

Esparza has a special mix including Latin music planned for her walkout. She wants to be an inspiration to a new generation of young females she observes training in gyms now across the country. "They're in there wearing sports bras and little training shorts and it's fine -- people accept that more now," she said. "It's great."

And what would Esparza tell a Latina of 11 years old walking into a boxing gym in south Texas today?

"You have a right to be there."

To read a version of this story en Español, click here to visit ESPNDeportes.com.