Colin Kaepernick grabbed headlines this week, working out and showing everyone in a widely shared video that he is in shape and capable of throwing a football. But the free agent quarterback has remained unsigned since he and the San Francisco 49ers parted in March 2017, with many believing that his social activism is keeping him out of the game.

That wasn’t lost on Eric Reid, the 49ers safety who joined Kaepernick in taking a knee during the national anthem to raise awareness of police brutality and racial injustice. Now he’s a free agent, too, and he believes that his activism is hurting him with owners.

“GMs aren’t the hold up broski. It’s ownership,” he wrote in response to a tweet. “People who know football know who can play. People who know me, know my character.”

The 26-year-old Reid, a 2013 first-round pick out of LSU, played some linebacker out of necessity in 2017; the Niners opted not to re-sign him when his four-year, $8.4 million contract expired.

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“The notion that I can be a great signing for your team for cheap, not because of my skill set but because I’ve protested systemic oppression, is ludicrous,” Reid wrote in another tweet. “If you think [it] is, then your mind-set is part of the problem too.”

Reid’s visibility as an activist grew last season, with Kaepernick out of the league and NFL player demonstrations drawing the ire of President Trump. Reid explained to The Post’s Kent Babb in October that he “was taught growing up that you always do what you believe.”

“A lot of it was taking Colin’s direction,” he said. “I told him how I felt and told him I wanted to support him, and from there we just kept talking and talking and talking, and here we are.”

Trump continued to direct attention to the demonstrations, and some players felt their pregame message was being misinterpreted as criticism of the military. Critics, meanwhile, argued that the protests were depressing NFL television ratings. Some players and NFL team owners sought to convert the sense of activism to action, and Reid was a visible member of the newly formed Players Coalition.

“Change in policies, change to the criminal justice system, just changes in our country overall,” Reid told Babb when he was asked what he would see as a satisfactory ending to his protest — which has grown to include dozens of NFL players and athletes in other sports. “We got here through decades and decades of the government prioritizing the needs of one group of people and de-prioritizing the needs of others.

“ . . . They target low-income families, families of color. Any change in policy moving forward is a start. It took hundreds of years to get where we are, so everything is not going to change tomorrow. But we can start today.”

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By December, as he no doubt knew he might be a free agent, Reid said he understood that his activism could cost him. It has, apparently, cost Kaepernick, with many asking if owners are blacklisting him.

“I would say I understand that’s a possibility and I’m completely fine with it,” Reid told ESPN. “The things that I’ve done, I stand by, and I’ve done that for my own personal beliefs. Like I said, I’m fine with whatever outcome happens because of that.”

That doesn’t mean he has to be quiet about it.

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