Super Nomario said:Risk / reward is part of it. I think the other thing is that teams can leverage changing non-guaranteed money to guaranteed money to clear cap space. Under the terms of the contract Brady signed in 2010, he was supposed to have a cap figure of $18.2 MM this year. They renegotiated in 2013, guaranteeing him $46 MM over the next five seasons, but lowering his cap figures over those years to between 13 - 15 MM. That's typical; teams clear cap space by renegotiating with the QB (usually the highest-paid player): the team gets short-term cap space, and the player gets more guarantees. If Wilson's deal is all guaranteed, the team effectively is shooting their bullets up front; it's not going to be as straight-forward to clear cap space later (if it's even legal) by modifying the contract.
(all numbers from http://patscap.com/brady.html#brady)
Presumably you could turn guaranteed salary into signing/roster bonuses--for example if he's guaranteed 16 million in 2016 you might still be able to convert some of that guaranty into a bonus at the beginning of the year, pay Wilson most of the money in a bonus rather than in 16 game checks, and pro rate the bonus over the remainder of the contract.
The big upside for a team is you save money, the downside is you end up with a player you can't cut. Is a 32 year old Russell Wilson in 2020 going to be worth $x million? Hard to say right now.