WATCH: Colin Kaepernick compares NFL training camps to slavery in new Netflix special

In a preview of a new Netflix special, former NFL player Colin Kaepernick compared NFL training camps to slavery.

In the clip, Kaepernick says of NFL owners and coaches: "What they don't want you to understand is what's being established is a power dynamic. Before they put you on the field, teams pose and examine searching for any defect that might affect your performance. No boundary respect, no dignity left intact."

The clip doesn't mention that this could be because owners and coaches are putting together teams of the highest athletic caliber possible, and that those players are then paid millions of dollars to play, with additional millions likely in advertising.

After Kaepernick's message, dramatized footage showing black athletically-built men being chained and sold by the edge of a cotton field is shown, with slave auctioneers visually compared to coaches and owners.

This dramatic footage also shows a coach and a slave auctioneer shaking hands, as it's the coach who is seen "buying" the players in chains from the side of the cotton field.

Kaepernick was an NFL player-turned-activist who popularized the notion of "taking a knee" on the field rather than stand with hand over heart for the American national anthem.

It was during a San Francisco 49ers pre-season game in 2016 that Kaepernick, the quarterback, refused to stand for the national anthem. This was in protest. He said: "I am not going to stand up to show pride in a flag for a country that oppresses black people and people of color. To me, this is bigger than football and it would be selfish on my part to look the other way. There are bodies in the street and people getting paid leave and getting away with murder."

He left the 49ers in March 2017 after becoming aware that the team was not planning to resign him. Kaepernick was famously not signed by another team.

Kaepernick played for the San Francisco from 2011 - 2016, and earned an average annual salary for several years of $19,000,000. His signing bonus alone for his rookie season was nearly $2.5 million.