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Unlike in the NBA and MLB, NFL players aren't guaranteed the entirety of their contracts. Sure, they're guaranteed part of it, but when a player signs a five-year, $100 million deal, he might only get $60 million guaranteed. Still a substantial amount of money, obviously, but if you compare that to MLB, it's a massive difference.

NFL players are unlikely to ever receive fully guaranteed contracts like other sports, given the frequency in which they get hurt or rapidly decline, which doesn't benefit them at all. However, with the salary cap ballooning each year, contracts are getting richer and richer with each passing season.

When the salary cap was instituted in 1994, it was set at $34.6 million. In each of the past four years, it's risen by at least $10 million, resulting in the cap being $167 million for 2017. That's a massive number, which is great for players. It means larger contracts and significantly more money than they were receiving 13 years ago.

No one's disputing that fact -- just look at A.J. Bouye's five-year, $67.5 million deal -- but why are some players settling for one-year deals? It's a trend that's become more evident in recent years, culminating in a boatload of "prove-it" contracts so far in this year's free agency.

It's especially notable among young players who are just entering their prime.

In 2013 and 2014, 13 players under the age of 30 signed a one-year contract worth at least $2 million. In 2015, there were 21. Last year, 17 players signed such contracts. In 2017, after about a week and a half into free agency, a whopping 24 players under 30 have already inked one-year deals worth at least $2 million.

Some of those players include Alshon Jeffery, Terrelle Pryor, Dontari Poe, Bennie Logan, Eddie Lacy, Prince Amukamara, and Morris Claiborne -- most of whom are former first- and second-round picks.

Part of the increase in the number of players has to do with the rising salary cap rising, but four years ago, it would have been unheard of for 24 players under 30 to sign one-year deals. That's a huge number.

Meanwhile, there hasn't been a single six-year contract handed out in free agency this year, compared to three in 2013, two in 2014, and one each in 2015 and 2016. Players are settling for shorter-term deals despite salaries increasing each year.

So what's with this recent trend? Well, it has to do with both the teams and the players. Teams have learned to protect themselves from destroying their salary cap with monstrous long-term deals. Gone are the days of Mario Williams' six-year, $96 million free-agency contract. Or Mike Wallace's five-year, $60 million deal with $30 million guaranteed -- which proved to be a flop of epic proportions.

Instead, you're seeing teams sign players to one-year deals. Jeffery, for example, signed a deal worth $9.5 million (with $4.5 million in incentives). He's just 27 years old. Pryor, by the same token, signed a one-year deal worth $6 million (plus $2 million in incentives). He's also just 27 years old. Those players are arguably both better than Wallace was when he signed his monstrosity of a deal, yet they settled for prove-it contracts.

But did they actually settle? Pryor said afterwards that he wanted a one-year deal.

"It's something that we asked for, myself and my agents, for a one-year deal," Pryor said last week. "It's kind of like a 'prove it' deal almost to a certain extent. I think a lot of people are thinking that this is a one-trick pony, like a one-time thing. You know, just out of nowhere I could catch 79 balls or whatever and go over 1,000 yards. I got a lot to prove and I really can't wait. I look forward to it."

Jeffery wasn't as forthright about his contract wishes, but he likely could have landed a long-term deal elsewhere. His baggage of injuries and questionable character likely hindered him from getting one, but he likely could have settled for less money annually while stretching it over several years, rather than just one.

It's impossible to know the intentions of a player in free agency, but if Pryor's comments are any indication, it seems as though they believe they can improve their value on prove-it contracts.

The cap is increasing by the year, which means more money will ultimately be available next offseason. That doesn't mean teams will be foolish and throw around money the way they did with Wallace, Williams and Albert Haynesworth, but contracts will ultimately be larger if those players perform at the expected level.

If Jeffery goes out and catches 90 passes for 1,400 yards and 10 touchdowns with the Eagles, his value will be far greater than it was this offseason. The same goes for Pryor, who reportedly turned down a long-term deal with the Browns in favor of Washington's one-year offer.

These short-term deals protect teams from hurting their cap situations for years down the line, while also guaranteeing players more money up front. For example, Pryor got all $6 million of his contract guaranteed up front with $2 million in potential incentives. Amukamara's $7 million deal was also fully guaranteed at signing.

Compare that to Kenny Britt, who's making $8.125 million per year, but his $17 million guaranteed is over four years. Pryor could have another 1,000-yard season in 2017 and land a deal worth far more than $17 million guaranteed, plus already have $6-8 million in his pocket.

Players would obviously prefer to secure their future financially with six-year, $100 million deals, but that's not the way the NFL works, and teams have quickly realized those contracts are often mistakes. Instead, they're betting on themselves with the goal of watching their finances rising with the ever-increasing salary cap. It's a win-win for both players and teams, and it often works out for both.

Last year, Nick Perry signed a one-year, $5.05 million deal with the Packers. This offseason, he signed a five-year, $59 million contract. Nick Fairley settled for $3 million for one season last year, while this offseason, he landed a four-year, $28 million deal. The same goes for Jared Cook and his $2.75 million "prove-it" deal a year ago, which earned him a $12.2 million payday with the Raiders a couple days ago.

Not every short-term deal works, but more often than not, it works in the player's favor. And that's why they're betting on themselves more and more each year.