The New England Patriots as well as the rest of the NFL will have several free agents set to hit the market in March. Free agency will begin at 4PM, March 9th. Teams can start to release players sometime in February 8th. Released veterans can then be immediately signed by another team while players with less than 4 accrued seasons go through the waiver season.
Some basic definitions –
Accrued Season
The number of accrued seasons determines the free agency status for the player. To gain an accrued season the player must be at full pay status for a minimum of 6 regular season games.