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Golfer Jim Furyk withdrew from a golf tournament in September, and Assani Fisher lost $70,000. Fisher, a professional daily fantasy sports player, has also made back nearly that much in National Football League games.

Fisher, 33, ranks among the elite in a booming industry where players buy into competitions and can make cash based on the performance of the athletic lineups they pick. Fisher, a former professional poker player, claims he turned $600 into $800,000 from February to September of this year playing games including golf, baseball and football. He put at least $150,000 on the line this past weekend alone.

Fisher and a select few others thrive in an industry that has become almost unavoidable for pro sports fans amid a barrage of ad spending and sponsorship from market leaders DraftKings and FanDuel. But the legally unique games now face a slew of criticism, sparked most recently by a New York Times story alleging that a DraftKings employee used nonpublic information to win $350,000 playing on FanDuel.

In a joint statement, DraftKings and FanDuel said "there is no evidence" that employees violated rules restricting them from using competitive data to play on rival sites. Both companies have temporarily banned employees from playing in online fantasy contests while they consider more detailed rules on employee participation.

The accusations have increased debate about more regulation of the fast-growing competitions, which unlike standard sports betting are mostly protected by federal law. The law varies by state, but fantasy sports generally are considered games of skill, so they're not regulated like gambling is. For Fisher and other gamblers turned fantasy sports pros, the distinction may not be that clear.

"It's somewhat ridiculous to call sports betting gambling and not daily fantasy sports gambling. Everyone really realizes it's gambling. It's a silly debate," Fisher said.

Daily fantasy games could generate an estimated $2.6 billion in entry fees this year, a 41 percent increase from last year, according to research firm Eilers Research. Amid the DraftKings and FanDuel advertisements that may encourage inexperienced players to jump in with the allure of big money, the industry has also come under criticism that most of the cash ends up in the hands of a few top players.

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"There are so many commercials, I think it's just a natural backlash," Fisher said. "Most people, I would say, should definitely just focus on having fun and don't go in thinking you're going to make millions of dollars."

Fisher, the seventh-ranked player in the world on fantasy site RotoGrinders, believes his professional poker experience lends itself to turning a profit in the "cutthroat" world of big-money fantasy sports. Seeking out beatable opponents and understanding risk come naturally to people with a gambling background, Fisher said.

Of course, putting tens of thousands of dollars on the line every week can bring some stress. Fisher spends about eight hours a day on fantasy. He does yoga while away from the games to reduce pressure.

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Monday's Times report has led to more scrutiny of the fantasy sports business model. It opens "monumental concerns" about how fantasy sports sites handle confidential information, said Marc Edelman, an associate professor of law at Baruch College who consults in fantasy sports law.

NFL agent Drew Rosenhaus also told CNBC on Tuesday that "there should be some regulation that maintains great integrity."

Disclosure: Comcast and NBC are investors in FanDuel.