Proving that a team or a league colluded to keep a player off the field has proved difficult over the years.
“Smoking gun” documents that show owners acted in a coordinated way are rare. Aggrieved players have a hard time proving teams deliberately passed them over in favor of less talented alternatives because teams hire and fire players for subjective reasons all the time, and are well within their rights to do so.
Then there is the case against the N.F.L. brought by Colin Kaepernick, the former San Francisco 49ers quarterback who has accused the league’s owners of snubbing him because of his decision to protest by kneeling during the national anthem.