Are NFL athletes employees of their teams, or are they contractors? Are their civil protections similar to a normal person working an office job?
NFL players are employees covered by a collective bargaining agreement negotiated by their union, the NFLPA, part of the AFL-CIO, which indicates specific different civil protections compared to an office job.
This is a two-way bargain, not categorically better or worse. On one hand, many office workers receive severance pay at the discretion of the employer; NFL players are entitled to specific dollar amounts based on service (Article 60 in the link above). On the other hand, in the event of a dispute, the union, speaking for employees, has agreed to defined arbitration processes instead of individual members being able to bring a lawsuit against the teams or leagues. This is of note as there was a union lockout in 2011. The union dissolved itself, and 10 players were able to bring a lawsuit against the league to challenge the lockout.
Decertifying the NFL Players Association enabled the players to file antitrust litigation against the owners, which they did late Friday, with superstar quarterbacks Tom Brady, Peyton Manning and Drew Brees among the 10 named plaintiffs.