Despite the decreased frequency in recent years, contract holdouts still crop up in the NFL. So why football and not so much in baseball, basketball and hockey?

Its all about the guaranteed money.

In Major League Baseball, the National Basketball Association and the National Hockey League, most contracts are guaranteed for the entire length of the deal. Not so in the NFL. Unlike the other major professional sports, NFL contracts rarely are fully guaranteed, and players routinely try to have contracts redone in an effort to secure more guaranteed money.

In most cases, guaranteed money in the NFL comes in signing bonuses. Players earn base salaries for each year of the contract, but those salaries are not guaranteed until the player makes the opening day roster in a given season. Thus, when players are not performing up to the standards expected of them, they often are released and are not entitled to the base salaries in the remaining years of the contract.

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