With a 39-0 career record, 30 knockouts, world championships in four weight classes and a happy family with three kids, Mikey Garcia could've played it safe.

He could've chosen his spots carefully over the next few years, maintaining an undefeated record by picking off the right opponents as he continued to build up his legacy and his bank account.

But that's not the way Garcia wanted to do it.

Rather than taking on another challenger who was closer in size, or a lesser fighter in a bigger division in order to get his legs underneath him as he climbed in weight, Garcia wanted to make the biggest splash he could think of by challenging Errol Spence Jr. -- a welterweight world champion with an undefeated record and dominant legacy of his own.

Garcia's family, his team and almost everyone around him told him not to take this fight, but Garcia persisted, and ultimately got his way. In an era when dream fights don't come together often, Garcia wanted to step forward and make a statement.

"It's funny because a lot of times with other careers, other fighters, they start off looking for legacy, looking for titles and at the end of the career, it changes," Garcia told ESPN ahead of Saturday's bout in Arlington, Texas. "It becomes more of a financial reason, it's a business. They look for the biggest, most lucrative fight, so they can make the biggest amount of money and take the biggest purse home, not necessarily for the titles.

"They don't really care about the titles -- they vacate that title at the moment to fight the guy that's going to make them the most money," Garcia continued. "But for me, it was kind of reversed. I did it early for the money and fine, I got a title -- it's not that important, it wasn't that special. Now, it's different. I've already had the money -- yes, there's a lot more that I can make -- but that's not why I'm doing it. I'm doing it to cement my name and add to my legacy and keep the Garcia name living for years to come."

Mikey Garcia challenged Errol Spence Jr. because that fight, in Garcia's mind, offers him a chance to cement his legacy in boxing. Luis Mejia/TGB Promotions

Preparing for this fight presented a lengthy list of challenges. Garcia's most recent outing, at lightweight against Robert Easter back in July, took place at 135 pounds. This welterweight championship fight against Spence will happen at 147 pounds.

Spence, on the other hand, has the body and frame that will one day allow him to compete all the way up to middleweight (160 pounds). By contrast, Garcia won his first professional title at 126 pounds.

Making weight is only one piece to the puzzle. With weigh-ins taking place more than 24 hours prior to the first bell, the opponent stepping on the scales on a Friday afternoon looks much different than the guy staring across the ring at you on Saturday evening.

"I'm probably going to be fighting a guy who will be outweighing me by about 12, [maybe] 16 pounds," Garcia said, "so I've got to be able to hold my own and be able to hold that size."

With this daunting task ahead of him, Garcia made a decision that dramatically altered his typical, more traditional approach to a fight. The 31-year-old wanted to take advantage of every tool at his disposal, and the allure of innovative science was too much for Garcia to resist.

With so much on the line, Mikey Garcia placed his confidence and his fate in the hands of Victor Conte.

"My first reaction was 12 pounds of muscle mass is a huge advantage," said Conte, recalling his immediate reaction. "In talking to Robert [Garcia Sr., Mikey's brother], he expressed that his dad [Eduardo] and others' initial reaction was they didn't want him to do this. They didn't think it was a good idea, either."

Just as he had convinced his family, Mikey quickly got Conte on board.

Mikey Garcia worked closely with coach Remi Korchemny (left) and Victor Conte to fold non-traditional training methods into his preparation for Errol Spence, Jr. Steve Kim for ESPN

Some might frown upon working with a name that might seem radioactive in the world of sports, recalling Conte's role with the Bay Area Laboratory Co-Operative -- better known by the infamous acronym BALCO -- and the steroid issues attached to baseball, track and field and many other sports, but the fighting world sees Conte in a different light.

For his part, before getting involved in such a high-profile fight, Conte made it clear that there would have to be stringent drug testing. Over the past decade, Conte has been focused on supplements and cutting-edge technology, while encouraging the strictest of drug testing for anyone he works with.

"We don't want to have any doubts that we're dirty -- that either one of us is doing anything," Garcia added.

Conte on his post-BALCO reputation Working with Victor Conte, who served a year in federal prison after BALCO was raided in 2003 for conspiracy to distribute steroids and money laundering, comes with some risk. For his part, Conte claims he is well aware of his reptutation and hopes that the work he's doing to help stricter enforcement will help to balance out past transgressions. "If I had to guess, I would say that 20 percent of the people out there will never be able to forgive me, this is just how it is, and I've learned to accept that. BALCO was 15 years ago and I've been an outspoken anti-doping advocate since 2005. It's been 13 years that I've been rattling people's cages. "I've met with all the various anti-doping agencies around the world, given them my input in trying to create a more level playing field for the young athletes of the future. I feel it's part of my restitution, I've contributed to sponsoring of many boxers, as well as MMA fighters, and I am just trying to, in my own way, make a contribution because I know that there was a time I helped to damage several sports. So I feel an obligation and it's something I feel I should do, to try to help create a more level playing field."

Garcia looked at the potential of what Conte was offering, and decided that his best path to defeating Spence traveled through Conte's operation.

Once the ink dried on the contract, Garcia, along with his nephew Robert Jr. and close friend Rafael Lopez, made the trek north from their home in Moreno Valley, California. They spent the next several weeks of their lives living out of a hotel just down the road from Conte's SNAC (Scientific Nutrition for Advanced Conditioning) facility in San Carlos, California and, with the exception of a single weekend trip home for his son Michael Angelo's birthday, they worked every day to improve.

Ahead of all of his previous fights, Garcia had always trained in a traditional fashion: early-morning jogs, hitting the gym in the late afternoon and then, as fight week approached, he cut down on food and liquid intake to make weight.

This time around, Garcia would kick off his fight prep with a far more modern approach that included intermittent hypoxic training. Hypoxic training simulates high-altitude conditions without the drawbacks of being in high-altitude climates, by creating an artificial atmosphere and utilizing manipulated oxygen levels. This style of training, first utilized by long-distance runners, causes the body to increase its production of red blood cells, which carry oxygen to the body.

During one particular training session at the SNAC gym, Garcia hit the heavy bag, something he has done thousands of time before in his life. This time, however, he did so while wearing a mask that was hooked up to a hypoxicator, which pumped air with a level of 14.5 percent oxygen into Garcia's system. Mike Bazzel, one of the staff trainers, explained that a normal level of oxygen at sea level is about 20.9 percent, with the mask simulating a much lower percentage, along the lines of what would exist at high altitude.

There's also a structure Conte calls "The SNAC Dome" -- a large bubble 18 feet in diameter and 12 feet in height. The structure has the ability to pump in an air mix as low as a 10 percent oxygen, which equates to around 20,000 feet elevation -- more than three times that of Big Bear Lake, the Southern California mountain town used as a training site by other fighters.

Inside Conte's dome, boxers like Garcia can work the mitts with their trainers, shadow box or do resistance training at these oxygen reduced levels, followed by intervals of recovery inside a smaller chamber with a 50 percent oxygen mix.

Oxygen manipulation is one part of the equation, to be sure, but another major element to Conte's training plan involves building up fast-twitch muscles in a way that ties closely into another sport he's long been associated with: track.

On one particular day at the nearby College of San Mateo, 86-year-old Remi Korchemny is barking out instructions like a drill sergeant to Garcia and a group of other boxers. Korchemny, a noted track coach and Conte's right-hand man, has a history of working with some of the best sprinters in the world.

More than 30 minutes were spent making sure the athletes were stretched out properly, so that they'd be able to perform the vigorous and detailed regimen Korchemny laid out. Then, for 90 minutes, the quartet of boxers executed the same drills and calisthenics Korchemny used with the likes of Dwain Chambers and Kelli White -- world-class sprinters who each, it should be said, saw careers scuttled because of their connections to BALCO.

"I've already had the money -- yes, there's a lot more that I can make -- but that's not why I'm doing it. I'm doing it to cement my name and add to my legacy and keep the Garcia name living for years to come." Mikey Garcia

Bleachers were climbed, and 20- and 40-yard dashes were run -- all at quick intervals meticulously timed and logged by Korchemny. The Russia native still has an athletic, lean profile, and isn't afraid to raise his voice as he exhorts the likes of Garcia to explode and accelerate into his sprints.

"It is a little different," Garcia said, during the early stages of his training. "First two days I felt real sick, I felt nasty. I felt like I was going to throw up. I felt like passing out. It's so different. But my body was able to adapt pretty quickly after those first initial two days. I was able to work through it.

"It's too early to say how much benefit I'm getting out of it, but I do feel already better than I was before."

The track workouts took place at the beginning of each week, as part of a meticulously planned process. Wednesdays were weight-training days, along with exercises with medicine balls and plyometric movements like box jumps. Fridays had scheduled hill training at Coyote Point Beach, with races on the beach between the boxers and repeat incline sprints.

Garcia's time at the SNAC facilities transitioned smoothly into Garcia's traditional boxing training as the fight drew closer. "The training that we did up there definitely helped." Luis Mejia/TGB Promotions

Other days were less vigorous, with the focus shifted to rest and rehabilitation in order to maximize output during more strenuous days. A lot of focus was also placed on building Garcia's body back up, utilizing hyperbaric chambers, pneumatic compression equipment and more traditional methods, such as intense sports massages.

"The training that they have for me, right now, is very focused on the explosiveness, fast-twitch, just being able to react quickly from one direction to another," Garcia explained before an evening session. "It's very high-intensity training, which in turn strengthens those parts of the body, those muscles, joints and ligaments.

"That will help me once I get in the ring, because that's what boxing is," Garcia continued. "I've got to jump in and out quickly, be able to avoid a certain corner, or maybe dodge a punch or whatever. You've got to react to it quickly and you've got to be able to counterpunch quickly. So the stuff that we're doing is just going to help in that way."

Conte and Korchemny have also designed more boxing-specific drills, taking everything they've learned from working with boxers such as middleweight champions Danny Jacobs and Demetrius Andrade to create equipment specifically designed to parallel movement in the ring.

During one morning's training session, Korchemny had the fighters punch while gripping two handles that were attached to bungee cords, while going back and forth on their feet. As they did this, they were instructed to be as quick and explosive as possible. After extending the cord, they were then told to move forward and throw punches, then slide back as they would in fight against an oncoming opponent, then quickly repeat the process.

"Faster forward!" implored Korchemny, emphasizing that he wanted Garcia to be sudden and rapid in his thrusts.

This movement, which simulates how a fighter will move into position to punch, is done by rotating from facing a very stiff breeze to fighting in quicksand. Doing this a few times taxes the legs, core and shoulders -- an exercise meant to make those actions easier and faster on fight night.

Saturday's fight will be the true test as to whether or not the extra work Mikey Garcia did was enough to push him to a victory over a significantly larger fighter in Errol Spence Jr. Frank Micelotta/FOX Sports

Garcia, who has never weighed more than 139.5 pounds for a fight, is unlikely to overpower Spence. For Garcia to pull off this upset, he must consistently be quicker than Spence and beat him to the punch -- and then sustain that tempo for 36 minutes.

Four months out from this IBF welterweight title fight, Garcia began preparing for what many believed to be an insurmountable task. For more than a month, through the holidays in December and the New Year, Garcia left his wife and three children behind to push his body to lengths it's never gone to before.

As the fight drew near, Garcia was confident in what he had gained from all of the preparation he put into this fight with Spence.

"The training that we did up there definitely helped," Garcia said. "We are going up in weight, obviously, so we needed to do a different type of training, I couldn't just sit back and do my regular routine at the gym."

Spence, the champion and the opponent at hand, was blunt in his assessment of Garcia's expanded efforts.

"I really think nothing of it. ... I don't think it's going to help him once he gets into the fight."

The action inside of the ring will ultimately show if that work was enough. And when Garcia spoke with the media, even a full month after leaving SNAC and returning to his brother's gym in Riverside, California, he drew from a deep well of confidence that's been building since late last year:

"I have no doubt that I'm going to be able to win this fight."