Welcome to the dilemma that the NFL owners are facing. There's a reason why they don't like the Collective Bargaining Agreement (CBA) that they have with the NFL Player's Association (NFLPA). It's because of these disparities that place HEAVY emphasis on potential rather than performance. That's the reason why the owners chose to not renew the contract.
A perfect example is Reggie Bush. He was the second overall pick, but he's making a fortune for riding bench and for visiting the doctor's office, while Thomas Pierre, a no namer who stepped up when he had to (see: 2007 Week 17 - CHI vs. NO) get's paid the minimum under the CBA.
Under the owners' agenda, the plan to set up such a system, where the contracts will be low on guaranteed money and stacked with incentive-based bonuses. This keeps players motivated, but mostly benefits team owners. This is why they chose to essentially remove the salary cap. Why is it that the NBA and MLB had no caps? Because they want to keep their players hungry (both metaphorically and somewhat literally). If someone doesn't pan out in the NFL, a team suffers for quite a bit (see: Browns with Tim Couch and Chargers with Ryan Leaf). The Cubs weren't too hot last two yea's but a methodical offseason has them looking great this season. The Celtics were jokes just last season, but look at how a blockbuster offseason allowed them to add another trophy to their already overflowing case.
However, the reason why the NFL is America's game is because of the fact that teams are literally built, not bought. Who ever thought Favre would be a legend? No one. Who believed that Tom Brady would step up once Drew Bledsoe went down? Not one person. How did the second last player drafted in a draft end up being the best reciever of that draft? Only Marques Colston believed. It's this salary cap that keeps teams together and makes the NFL so endeared. By switching to performance based contracts, the TOTAL salary of a team can fluctuate and leave teams that were healthily under the cap space either pressing up against it or even go over, if they have a dominant season. Such a system would require the removal of the salary cap, which is why the owners basically dissed the NFLPA. So in that respect, this system is being set up as we speak.
However, I like the current system because it keeps teams from being bought or built through blockbuster deals. It's the only sport I feel that requires ALL the players to do their part. John Lynch could've gone to the Jets and be paid handsomely, but he decided to join the Patriots because he'd much rather be part of a team than a locker room filled with individuals, which is what a performance-based system creates. Players have begun to felt the squeeze of this new system, which is why it seems that almost everyone is vying for more guaranteed money on their current contracts. Anquan Boldin has all the right to be angry. How is Larry Fitzgerald, an injury prone WR, able to make more than him, especially after he's put up with the team longer than him, and he doesn't get preference over him. They put their necks on the line EVERY play, and could be out of the game that helped them get where they got on one of them. Under a performance based contract, they would only be paid for the practices, OTA's, camps and games they attended. It could ruin their lives! I'm an advocate for the players, so I feel that if something ain't broke, don't fix it. But at the same time, make sure that it's running well and keep it in maintenance. The owners didn't, which is why there's this rift between incentive-based and guaranteed money contracts. A contract with a balance of both is the best recourse. Matt Ryan isn't worth the 70+ million dollars, especially as a rookie. But at the same time, that's the worth of his contract. Who knows if he'll even be able to make the "guaranteed" money because all it takes is an injury. There's my two cents. =]