RUBALCADA HAD everyone fooled.

Walters' big action is unwelcome in many sportsbooks in Vegas, so he relies on his network of "runners" like Rubalcada, who are tasked with placing bets without giving any hint that they're working for someone else.

"When I was first introduced to [Walters], he told me, 'This is the first and the last time you'll ever see me,'" Rubalcada says. "He was like, 'If they see you with me, you are no good to me.'"

Vegas sportsbooks fear losing huge to top gamblers, so many set limits of $10,000 on college and $20,000 on NFL games. Meanwhile, an account that's too successful runs the risk of being shut down. That makes a large network a major advantage -- each runner stays under the limit, but the total amount bet on Walters' behalf often exceeds it many times over.

"There are some groups out there that bet an awful lot of money, but they don't do it at anywhere near the sophistication," says David Malinsky, a longtime handicapper who says he previously worked for Walters evaluating teams and analyzing games. "They can put the network together of picking the games and having the handicappers. But they can't build out that distribution network."

So Rubalcada spent day after day in the dimly lit sportsbook, waiting to hear from a guy nicknamed Wolf, whose urgent messages would arrive shortly before kickoff or tip-off. Rubalcada would instantly punch in bets on an M Resort tablet linked to his account.

"He never came across like he was betting for Billy or anybody else," says Mike Miller, the M's former risk management supervisor. "He was acting like it was all his money."

But in fact, Rubalcada wasn't even always trying to win, though he didn't know it at the time. Eventually, he grew to understand one of Walters' keys to success: Some of his bets were intentional losers, designed to manipulate the bookmakers' odds. Walters might bet $50,000 on a team giving 3 points, then $75,000 more on the same team when the line reaches 3.5. The moment the line gets to 4, a runner is instructed to immediately place a larger bet -- perhaps $250,000 -- on the other team. The $125,000 on the initial lines will be lost, but if things go according to plan, the $250,000 on the other side will win enough to make up for it many times over. Walters uses the same method on multiple games, often risking millions each weekend.

Walter's Legal Troubles 1982 Walters pleads guilty to misdemeanor bookmaking in Kentucky. He is sentenced to six months' probation and a $1,000 fine. 1985 The FBI raids 45 homes in 16 states, launching a case against Walters and other members of the Computer Group. 1990 Walters and his Computer Group associates are charged two weeks before the five-year statute of limitations is set to expire. 1992 Walters and his Computer Group colleagues are acquitted of conspiracy and illegal transmission of wagering information. 1996 State agents raid Walters' Sierra Sports Consulting. Walters and three other defendants are later indicted for money laundering. 2002 The money-laundering indictments against Walters and his three co-defendants are dismissed by a local judge. 2014 Walters, pro golfer Phil Mickelson and investor Carl Icahn are reported to be under investigation for insider trading.

Since the days of the Computer Group, analytically inclined professional gamblers have relied on technology as well as research to produce what is called a delta: the difference between the Vegas line and what the bettors conclude the point spread should be. The greater the delta, the more money a gambler like Walters will bet. There's nothing illegal about manipulating lines, and many prominent gamblers have the ability to move a line with as little as $1,000. Walters' strategy is simply more sophisticated and uses more people, better information and, of course, more dollars bet in far more places than anyone else's, insiders say.

Walter's Legal Troubles 1982 Walters pleads guilty to misdemeanor bookmaking in Kentucky. He is sentenced to six months' probation and a $1,000 fine. 1985 The FBI raids 45 homes in 16 states, launching a case against Walters and other members of the Computer Group. 1990 Walters and his Computer Group associates are charged two weeks before the five-year statute of limitations is set to expire. 1992 Walters and his Computer Group colleagues are acquitted of conspiracy and illegal transmission of wagering information. 1996 State agents raid Walters' Sierra Sports Consulting. Walters and three other defendants are later indicted for money laundering. 2002 The money-laundering indictments against Walters and his three co-defendants are dismissed by a local judge. 2014 Walters, pro golfer Phil Mickelson and investor Carl Icahn are reported to be under investigation for insider trading.

The work starts well in advance of a game. Malinsky, who says he worked for Walters on two occasions as a college football handicapper, says he routinely provided Walters quantified evaluations of teams, broken down by color codes and letter grades. Walters had similar arrangements with others who handicapped NFL, NBA and college basketball games.

The vast Walters network also includes a guy on the East Coast known as The Reader, who scans local newspapers, websites, blogs and Twitter for revealing tidbits or injury updates. That information is weighed and plugged into the computer alongside other statistical data -- from field conditions to intricate breakdowns of officiating crews. Armed with algorithms and probability theories, the objective is to find the mispriced team, then hammer the line to where Walters wants it.

"What Billy is also able to do is handicap the handicappers," says Malinsky, now the editor-in-chief of news for Pregame.com, a Vegas-based website selling handicapping information. "So after a while he knows what this type of game from this guy is worth. He will just absorb the information and then make the final decision. He is the coach calling the plays."

Asked about Malinsky's descriptions, Walters says, "He has no clue how my operation runs. Unfortunately, David wasn't successful in what he did, and I discontinued the relationship."

Rubalcada, in his position as a runner, didn't know the details of how any bets came together. Rubalcada says he made his way into Walters' world booking tee times at Royal Links Golf Club, a pricey course Walters owns a few miles off the Strip. Rubalcada says he advanced to a job best described as course hustler, setting up on a par-3 hole with his pitching wedge and offering foursomes the chance to wager on who would make it closest to the pin.

When Walters' gambling operation offered him a job, Rubalcada saw a chance to make huge money. Eventually, he began mimicking some of Walters' betting action with his own funds, relying on an inside source to text whether Walters' bets were real or phony moves. It didn't always work, and Rubalcada dug himself a hole so deep that he began embezzling from his Walters-funded account, taking a total of $482,833. He added to his troubles when he attempted to cover the theft by staging a carjacking, which was captured on hotel video surveillance.

Rubalcada eventually pleaded guilty to two felony theft counts and last March was sentenced to three years' probation and ordered to make restitution of $364,634. "I'll be dead before they get that money back," he says. In the fall, his legal woes escalated when he was jailed for violating the terms of his probation, which included random drug testing and prohibitions on alcohol use and gambling. Rubalcada, who drank heavily during two ESPN interviews, remains in jail awaiting a spot at a drug treatment facility.

After Rubalcada was arrested, one of Walters' attorneys visited the county prosecutor's office -- without prodding -- armed with records detailing how the gambling operation was set up legitimately through a limited liability corporation. The move surprised and impressed authorities, as did the fact that a former Vegas detective was overseeing the group's security arm. "They had one of the biggest law firms in the city set up their entire corporation and their books," says Brian Rutledge, Clark County's chief deputy district attorney. "It was scrupulously set up to be in compliance with all the gaming regulations. They were better set up legally than your average business, let's put it that way."

EVEN THE GREATEST gambler of all time doesn't always win -- but he doesn't have to. In the sports gambling world, where the house takes a 10 percent cut, bettors need to win 52.38 percent of their games to break even. Any additional wins represent pure profit -- and when hundreds of thousands of dollars are wagered on a single game, lots of it.

"The average guy on the street might be disillusioned if he knew the actual winning percentage," Malinsky says of Walters' consistent but seemingly modest success against the line. "What people don't understand is that the difference between winning 53 percent and 55 percent is like swimming the Atlantic Ocean."

Walters gets those extra 2 percentage points and sometimes much more. He has boasted that he has suffered only one losing season in 39 years, and past criminal investigations provide a snapshot of his success. The 1985 raid against the Computer Group revealed that the syndicate won an eye-popping 60.3 percent of its college football picks one season. More recently, an unsuccessful money-laundering case in 2002 found that Walters was consistently winning as much as 58 percent a week, sources told ESPN. This year, Walters says, he expects to break even. "Quite frankly, this may be my last year," he says. "I may not do this anymore."

Another myth about professional gambling is that every big bet is made in Vegas. Placing bets outside Nevada is a legal gray area and, as a result, a subject on which those close to Walters refuse to shed much light. But multiple sources estimate that only a small fraction of Walters' bets are actually placed there. The remainder, they say, happen either at offshore gambling sites or, to a lesser extent, through a network of bookies, many of whom have had relationships with Walters for decades.

Sources say Walters' operation has become more active in offshore sportsbooks, in Europe and in the emerging Asian market. A 1996 raid on Walters' office found more than 40 telephones, from which authorities said more than 12,000 long-distance calls a month were placed to illegal bookmakers in the U.S., Canada, Central America and the Caribbean. Additionally, documents detail a wire transfer of $970,000 -- suspected by authorities at the time of being "illegal gaming winnings" -- into Walters' Las Vegas bank account through banks in Montreal, London and New York. Walters was indicted three times for money laundering in connection with the investigation, but the charges were dropped before trial.

Today, sources say, the headquarters of Walters' international operation is located outside the United States. The last known location was in Panama, according to sources, after earlier offices were based in London, the Bahamas and Tijuana, Mexico. "Very little happens here," one source familiar with Walters' operation says of the group's Vegas-based gambling.

FEW PEOPLE HAVE experienced the many facets of Walters' personality as intimately as John Mastronardo, a convicted gambler and the younger brother of one of the country's biggest bookies. Mastronardo, who says he worked for Walters from 2000 to 2005, calls his former boss a genius. But he also witnessed what he saw as a dark side -- Walters could be cunning and openly malicious, he says.

Mastronardo, who has also dabbled as a bookie and worked in the Caribbean as an offshore sportsbook operator, says he and 20 or so underlings moved bets for Walters from Philadelphia before he moved to Las Vegas to work out of Walters' headquarters in exchange for a 25 percent cut of the winnings. "At times, he would give me $1 million to hold, $2 million to hold, with no signed contract," Mastronardo says. "I was betting it for him, so he staked me a bankroll."

Holding court in his airy fifth-floor beach condo in Boca Raton, Florida, Mastronardo, 59, looks fit and tanned, like he just walked off the golf course. But any day now, he will settle into a federal prison for a nine-month stay, the price for pleading guilty last year to illegal gambling and racketeering charges in connection with his post-Walters operation.

While many former associates fear speaking openly about Walters' business, Mastronardo says he has little to be afraid of. Talking about his past work helps ease some of the pain and embarrassment he's caused his family after more than 15 arrests, he says, adding that he's sought counseling to overcome his shame.

Mastronardo, an All-American wide receiver at Villanova and 10th-round pick of the Philadelphia Eagles in 1977, says he first met Walters in the 1980s while playing in a golf tournament for high-rolling gamblers hosted by Jack Binion, who owned a large casino in Vegas. Nearly two decades later, he says, the connection paid off when Walters asked him to move games.

One of Walters' major advantages, Mastronardo says, is his focus on smaller college games, which don't attract much action and thus often aren't researched as deeply by bookmakers. "Where they used to make a lot of money was on what they used to consider write-in games, that small college game where I didn't even know they had a line on it," Mastronardo says. "You might have a 7-point favorite with two no-name teams and the underdog would win by 15. Billy's art was to keep that game close to 7 and bet as much as you can without the world finding out about it."

One memorable night, Mastronardo says, he was at dinner with Walters and his wife when Walters began asking about a basketball game. "He says, 'What did that Old Dominion game open at?' I said '1.' He says, 'What did it close?' I said '1.' He says, 'I put $250,000 on Old Dominion tonight, and nobody knows about it.'

"That to me is genius," Mastronardo continues. "First of all, nobody knows where he bet it. Now you can bet in foreign markets. Some he bets in the casino. Some he bets offshore. Some he bets in different markets. So he uses the market however he wants. But the art was that he could bet a game for a lot of money and nobody would know about it."

But there were reminders that Walters could also be ruthless. Mastronardo recalls flying first class to Vegas with a duffel bag stuffed with more than $200,000 in cash for Walters. Federal agents stopped him before he could leave the bustling McCarran airport terminal and began pressing him to turn over the money, which they suspected was earned illegally. Mastronardo managed to get a message to Walters through Fats, a driver sent to the airport to pick him up. The reply from Walters was matter-of-fact: "Tell John good luck."

After several hours of questioning, agents accepted Mastronardo's defense that he was a professional gambler and allowed him to leave with the money. But the next morning, after Walters got his cash, he issued Mastronardo a warning: "He says, 'Johnny, you know the rules, right?' He says, 'That money was for me. If I don't get the money, it means I didn't receive the money. It means you are on the hook.' And he is right. That is the way it is."

Years later, when Mastronardo was operating an offshore sportsbook, he believes Walters planted a whale -- betting parlance for a high roller -- to hit his business. The suspect was a well-known Hollywood star who wanted to bet $100,000 a game, though Mastronardo became convinced that the actor didn't know anything about football. But after about three weeks, the man was winning so often that Mastronardo shut down his account, suspecting Walters had smartened him up.

"Billy knew it was me, and I used to have a relationship. But it is all fair in love and war," Mastronardo says, shaking his head. "Billy is very, very smart. And he is very cunning. He is kind of like a boxer you don't like personally but you respect his skill. Tiger Woods in his prime. You don't like the person, but you like the golfer."

For his part, Walters says he hasn't spoken with Mastronardo in 15 years. "Well, I don't recall him moving any money for me," he says. "I do know John Mastronardo. I don't recall having any relationship with him. He was a gambler, bet on sports, good golfer and a very personable guy."