Former sports agent and current NFL salary cap expert Joel Corry (@corryjoel) put up an interesting column at CBS on Monday detailing how all 32 NFL teams structure player contracts. There are four basic structures. Here's how the Eagles operate, per Corry:
The Eagles typically employ the signing bonus/base salary guarantee structure. The first two years of base salary are fully guaranteed, except with LeSean McCoy whose third-year base salary (2014) is fully guaranteed. It would be a surprise if Philadelphia did another deal where the guarantees didn't have offsets because Nnamdi Asomugha made $4 million from the team last year after he was released thanks to a 2013 salary guarantee without offsets.
This structure was recently apparent in a number of deals the Eagles handed out this offseason. And once again we see how Nnamdi Asomugha was a learning lesson for the Eagles in more ways than one. Here's a more detailed description of the contract structure that the Eagles use:
Signing bonus and salary guarantees
Guaranteed money with this structure consists of a signing bonus and salary guarantees. The base salary in the first contract year is usually fully guaranteed (injury, salary cap and skill guarantees) at signing. Roster bonuses in the first contract year due a few days after signing are fairly common. Even though these roster bonuses technically aren't guaranteed, they are considered as a part of the guaranteed money. Salary guarantees in subsequent contract years are mainly base salary. Some teams will fully guarantee the second-year base salary at signing.
The trend is for base salaries after the first contract year to be conditionally guaranteed. They are guaranteed for injury only initially but fully guaranteed if a player is on the team's roster on a specified date in each specific contract year. This date will vary from team to team but is normally within the first few days of the current league year (i.e.; 2015 base salary becomes guaranteed on third day of the 2015 league year). Early roster bonuses (first day of the league year) in subsequent contract years containing guarantees aren't as common as the base salary guarantees but operate in a similar manner.
A majority of salary guarantees have offset language. An offset clause reduces the guaranteed money a team owes a player when he is released by the amount of his new deal with another team. Without an offset, the player receives his salary from the team that released him as well as the full salary from his new contract with another club.
The Eagles have been fairly successful with this structure. They managed to avoid cap trouble and have enough money to keep their own players and/or sign free agents. The Eagles currently have the 6th most cap space in the NFL (nearly $19.5 million) and are likely saving it so they can roll it over for 2015 when a number of young players (Nick Foles, Fletcher Cox, etc.) are eligible for contract extensions. Keep in mind it's likely that those extensions will follow the structure Corry detailed above.