The National Football League (NFL) has launched a pay-to-play fantasy football game in 43 states, becoming the first major US league to embrace the 'gambling' concept.
NFL Fantasy Ultimate Experience Leagues offer prizes such as NFL game-used balls to league winners.
Entrance fees will vary from $4.99 to $124.99.
The new paid format means the NFL must comply with state gambling laws, whereby any contest is deemed to be illegal if it involves three elements: consideration (an entry fee), reward and chance.
To this end, NFL lawyers have prohibited entrants in seven states where the outcome of a fantasy football league might be construed to be affected by 'chance'.
The new format appears to be the NFL's attempt to harness a corner of the 'derivative' fantasy football market, whose revenue far outstrips its own.
The NFL has annual revenues of $10bn, while Forbes value the fantasy football market at $70bn.
However the league faces accusations of hypocrisy, as the NFL recently sued New Jersey to prevent the state legalising sports betting.
NFL commissioner Roger Goodell wrote in his statement for the case: "The core entertainment value of fair and honest competition between teams and athletes will be replaced by the bettor's interest, based not on team or player performance, but on the potential financial impact of each on-the-field event."
Washington D.C.-based newspaper The Hill reported on Tuesday that the Fantasy Sports Trade Association had hired a lobbying firm to monitor "legislation related to gaming".