Colin Kapernik is suing the owners of the NFL team, whom he believes are plotting not to hire him because of his protests against racial injustice.
The 29-year-old has been without a team since quitting his contract with the San Francisco 49ers in March.
Colin Copernicus protested for the first time, sitting during the national anthem in August 2016, before choosing to kneel instead.
Other players followed suit, and criticism of President Donald Trump this September saw protests spread.
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In a statement published on October 15, Colin Copernicus’ lawyers wrote: “We can confirm that this morning we filed a complaint with the CBA on behalf of Colin Copernicus.
“This was done only after pursuing all possible paths with all NFL teams and their leaders.
“If the NFL (like all professional sports leagues) remains a meritocracy, then the principled and peaceful political protest – which the owners themselves made a great theater imitating weeks ago – should not be punished and athletes should not be denied jobs.
“Such a precedent threatens all patriotic Americans and goes back to our darkest days as a nation. Protecting all athletes from such covert behavior is what forced Mr Kaepernick to file his complaint.
“Colin Copernicus’ goal has always been and remains simply to be treated fairly by the league for which he has performed at the highest level and to return to the football field.”
Some 49ers players knelt again during the anthem before their game on October 15.
They played for the first time since Vice President Mike Pence left his game in Indianapolis after several team members failed.