Houston Texans defensive end J.J. Watt, the best defensive player in the NFL, is set to sign a six-year contract extension.

The extension is said to be worth $100 million, but it's really not. NFL contracts are rarely what they seem, and Watt's is no exception.

The deal contains $51.8 million in injury guarantees, according to Jason La Canfora of CBS Sports.

$30.8 million is fully guaranteed up front, La Canfora reports.

The other $21 million in guaranteed money only becomes fully guaranteed (meaning he'd get paid even if the team cut him) at the start of the 2016 season.

That means the Texans can hypothetically cut Watt after this year or next year and only pay him $30.8 million total. If Watt suffered a career-ending injury in the next two years, though, he'd get the full $51.8 million.

The $51.8 million in injury guarantees is the most ever given to a defensive player.

The contract highlights some of the absurdities of NFL contracts. If Watt were a baseball or basketball player, he would sign his monster $100 million contract and make every penny of it, no matter what. Instead, he has to stay productive until 2016 to even earn half of what people are calling "guaranteed money," and after that the team can cut him at its earliest convenience without him seeing a penny more than the $51.8 million in fully guaranteed money.

History tells us Watt will get cut or be forced to restructure his deal before he comes anywhere close to $100 million.

The NFL is the country's richest, most popular league. It's also the league where players are most disposable. Even for guys like Watt who are at the absolute high end of the NFL totem pole, the contracts are worth significantly less than advertised.