Last season, the NFLPA filed a grievance with the NFL on Reid's behalf, alleging that team owners and the league, influenced by President Donald Trump, colluded to prevent his employment because of his protests.
The Panthers had a need at the position after veteran Da'Norris Searcy was placed on injured reserve last week after suffering his second concussion in a month. Carolina played with a three-safety rotation on Sunday against Cincinnati, starting Mike Adams at strong safety and Colin Jones at free, with rookie Rashaan Gaulden giving relief.
The Panthers next play against the New York Giants on Oct.