At a K-Mart in Pomona, CA, a green-eyed cashier was working the register for about $5.50 an hour. Back in 1996, this was decent money compared to the 26-year-old's job moonlighting as an undefeated top contender for the IBF lightweight title. He would eventually quit the job, giving his boss a year's notice in the form of three accurate predictions: "In about a year, I'm going to be world champion. You're going to read about me. I'm going to have millions of dollars." Shane Mosley was met with doubt that day. He often has been ever since.

A year ago, Mosley, now 38, was an over-the-hill underdog challenging the WBA welterweight champion Antonio Margarito. "After the first body shot landed in the first round," Mosley says, "I knew I had him." In the final seconds of the eighth, Margarito doubled-over from a left to the solar plexus, pushing Mosley aside so he could perform a face-plant onto the canvas. As Mosley's barrage of overhands and hooks continued in the ninth, the ref stepped in, appearing less to stop a fight than to save Margarito's life.

On January 30, Mosley was to face Andre Berto, who withdrew from the fight to be with his family following the earthquake in Haiti. That bout has now been eclipsed by a May 1 date with the undefeated Floyd Mayweather Jr. - and Mosley is ready.

For all but four of his previous 51 fights, Mosley's trainer was his father Jack. The night against Margarito, however, it was a 45-year-old orthodox Muslim from Philadelphia, Naazim Richardson. Since suffering a stroke in 2007, Richardson rehabilitated his own health, and then did the same for the careers of Shane Mosley and Bernard Hopkins. Mosley explains, "You can't use everything in your arsenal every time out, and Naazim points out things I'm not using that I forgot were there." It is Richardson's aim to focus on steady progress for each of Mosley's fights in 2010, saying, "I want the last opponent to say, 'S**t, I wish I could have gotten the Margarito ass-whupping.'"

The resurrection of Mosley's dominance secured his fifth world title, but also endless frustration. For months, he crusaded unsuccessfully to land a date against either warlord of boxing's pound-for-pound kingdom: Manny Pacquiao or Floyd Mayweather. To plead his case, Mosley drove to Pacquiao's gym and stormed the ring to confront Mayweather just after his defeat of Juan Manuel Marquez. Both men have refused to fight Mosley (or each other for that matter), and consequently the new welterweight champion spent the rest of 2009 outside the ring.

Mosley does not believe, however, that Pacquiao is ducking him, suspecting the Filipino's trainer is more at fault, "Pacquiao's a real warrior -- Freddie Roach is more afraid of me than Pacquiao." And now with a confirmed Mayweather date, Mosley can no longer jibe the fighter for being afraid.
 
Mosley believes in the science of boxing. He has no superstitions. Unlike nearly all fighters, Mosley does not even have a fixed rule for when he cuts off sex during training. (He says a month before is ideal, although he confesses, "when I fought Oscar the first time, I did it the night before.") A student of the game, Mosley can mimic the styles of other elite boxers at will. While watching footage of Pernell Whitaker against Greg Haugen (which seems to be the champ's idea of a good time), Mosley stood up and mimed Whitaker, Mayweather, and Berto.

In the garage of a home tucked in the snow-capped hills of Big Bear, CA, Mosley's customized gym is where the fighter hones his skills in hopes of being just good enough. For nearly a decade, he has trained here, over 200 miles from his residence in Las Vegas. The altitude lends an escape from distractions, which for his last fight were extensive: a divorce that finalized during his training and the aftermath of Mosley's involvement in the BALCO steroids scandal. He shut them out of his mind when he entered the Staples Center last year.

In the past, Mosley has learned to fight through plenty of other obstacles: a broken knuckle in his first victory over Oscar De La Hoya, blood blisters on his feet against Ricardo Mayorga, and twice with a hernia-once against Adrian Stone whom he knocked out in three and the next bout (his first loss) against Vernon Forrest. When the latter landed a low blow at 1:27 of the 10th, Mosley's cup dug up into his hernia. Buckling over towards Forrest's uppercut, Mosley recalls thinking to himself, "F**k that. You're not stopping me. You're not knocking me out." Mosley shakes his head at the memory, "The will is crazy." Besides, more than 20 years ago, Mosley had already fought through far greater anguish, both physical and emotional.

In the late 1980s, during the week of the Golden Gloves state tournament, Mosley was driving with his three year old nephew, Diamond. As Mosley pulled onto the freeway, the car's back wheels spun out of control leaving the on-ramp, causing the car to flip. Neither passenger was wearing a seatbelt. While the roof collapsed into Mosley's head and neck, Diamond fell through the passenger side window, after which the vehicle crushed him. Mosley remembers, "I was there with the police when the car was pulled up and he was there underneath, eyes shut, with dirt in his mouth. It was horrible. It was the worst thing that has ever happened to me." Struggling to set the trauma and physical pain aside, Mosley fought later that week, winning his bout.

The day after Mosley recounted this story, his fight with Berto fell apart. Just a week earlier, in Big Bear, weigh-ins and strokes were both held in contempt as Mosley devoured a Reuben sandwich and Richardson inhaled some corned beef followed by downing a bowl of beef chili. After this, they trained. Shirtless, Mosley sported a new Maori warrior tattoo on his left arm as the pair worked mitts. In an unorthodox decision, Mosley then kept on his gloves for the speedbag, which he hit with mesmerizing focus. It's this self-reliance that brought Mosley to the sweet science, believing, "With team sports, you can always blame losing on someone else, but with boxing I always thought, 'Nobody can beat me if it's just me.'" If he dispatches Mayweather, it may not be long before Mosley has no one left to beat, but he will still be in the gym -- alone, shadowboxing, knowing someone somewhere is doubting him.

(This story first appeared on HBO.com in advance of the cancelled January Mosley/Berto match.)

Mosley believes in the science of boxing. He has no superstitions. Unlike nearly all fighters, Mosley does not even have a fixed rule for when he cuts off sex during training. (He says a month before is ideal, although he confesses, "when I fought Oscar the first time, I did it the night before.")