There is an obscure provision of the NFL collective bargaining agreement (Article 21, Section 9) which allows players who received a tender but haven’t signed an NFL contract, and unrestricted free agents whose contracts expired to participate in offseason workouts and minicamps with their previous team while retaining their free agency rights.
The NFL and NFLPA recently came up with standard language to cover such players (Appendix Q to the collective bargaining agreement). This new Appendix Q protects players in case they are injured while participating in team activities during the offseason. In the case of an injury, a player will receive as a one-year salary the greater of his required tender, his applicable minimum salary or the amount negotiated by the player and the team. Participation by a player is voluntarily under this provision so he can withdraw at any time with impunity.
Wallace is free to work out with the Steelers, but that doesn't guarantee he'll be playing in Pittsburgh next season.
From a practical standpoint, players who are franchised, such as Drew Brees and Matt Forte, and restricted free agents, like Mike Wallace, can choose to participate in team activities without signing an NFL player contract. In Forte's case, his 2012 salary would be $7.742 million with an injury, his franchise tender, since it’s unlikely that the Chicago Bears would agree to a greater amount in order to get him to take part in the offseason workouts.
A main benefit to signing a participation agreement instead of an NFL contract is that a player will preserve his option of holding out without subjecting himself to penalties.
