The most talked-about N.F.L. player this season may not even be taking the field.

The player, Colin Kaepernick, a former quarterback for the San Francisco 49ers, caused conflict last season by kneeling during the national anthem before games to protest police brutality and racial oppression. He inspired several other players to follow suit or make similar gestures, leading to debate about whether athletes should publicly engage in political discourse — and how actively.

But now, as teams prepare for the start of the regular season on Sept. 7, Kaepernick is a free agent without a team. And while he is not at the top of his game, as he was when he led the 49ers to the Super Bowl four years ago, many analysts believe teams are refusing to sign him because of his political nature, not his ability.

With the nation consumed by racial division and discussion, the Kaepernick protests have spread beyond football, drawing more people not associated with the sport to speak out.