The Pats can avoid Gaffney's $500k+ base salaries (increasing) for the 2016 season and beyond from his original contract by waiving him. Bet they re-signed him to something cheaper--an injury-filled past like Gaffney's is not attractive to many teams :(
The Pats probably got him for cheap then, naturally. Here's hoping Gaffney makes a splash this year--the Pats are full of injured or not-well-rounded backs iirc.