(Marcio Jose Sanchez/Associated Press)

In hushed tones this spring, as the free agency period crept along, NFL team personnel executives anonymously said that Colin Kaepernick’s continued unemployment boiled down to talent and skill and work ethic. Training camps have opened, and to many it’s becoming harder to deny that something else might be at play.

“The players have spoken up enough. The media has spoken up. It just takes the ownership for someone to say we want this guy in our locker room,” Seahawks defensive end Michael Bennett told reporters in Seattle on Thursday. “. . . It’s crazy to see this guy not have an opportunity in the NFL. It’s just weird. I mean, some quarterbacks, as we all know, shouldn’t be playing, but they are, and this guy is sitting on the side. We all know why. It’s just hard to fathom that he’s not having a job this year.”

The NFL has accepted characters of all stripes over the years. But Kaepernick took a knee during the national anthem last year, a personal form of protest, he said, against police brutality of African Americans and other minorities. His action was met with equal parts enthusiasm and outrage across the country, but the continued backlash he faces seems to say as much about the NFL as it does about the polarizing quarterback.

“I don’t know what his status is in the NFL, but I’m glad the NBA doesn’t have a politician litmus test for our players,” Dallas Mavericks owner Mark Cuban said. “I’d like to think we encourage our players to exercise their constitutional rights.”

Far beyond the shape of the ball or the size of the players, there’s a cultural divide that distinguishes professional football and basketball in the United States. Set in contrast to the NBA, the NFL has struggled at times with how to treat players who court controversy, worried about the reaction from fans and sponsors. In the NBA, everyone from players and coaches to owners and league executives has shown a willingness to tackle hot-button issues, regardless of who might be offended.

“Everything starts from the top,” said ESPN analyst Jeff Van Gundy, a former NBA coach. “Commissioner [Adam] Silver embraces all kinds of different ways of thinking. I think he encourages activism. And because of that, I believe, some of our players in the NBA feel very empowered to speak their mind.

“That’s healthy that we embrace different thoughts. You can agree with Kaepernick, you can disagree with Kaepernick, but what I don’t think you should believe is that he doesn’t have the right or he should be muzzled in any way.”

While pundits and Kaepernick supporters accuse the NFL of blackballing an outspoken player, team executives have defended their personnel decisions, saying in essence that if Kaepernick could help a team win, he would be in a training camp right now.

“I feel that every team in the National Football League makes every decision on players to win the ballgame,” Dallas Cowboys owner Jerry Jones said Saturday. “And so if someone is not on a team, I would say that for whatever the reason, the decision-makers on all 32 teams are trying to pick them to win. And so I accept that. And if they’re not out there, that’s why they’re not out there.”

Kaepernick, 29, who became a free agent in March after opting out of his contract with the San Francisco 49ers, started 11 games last season, completing 59.2 percent of his passes for 16 touchdowns and four interceptions . It was a respectable year statistically, but the 49ers finished with only two wins in 16 games and his play, which has declined since he led San Francisco to the Super Bowl in 2013, again came under criticism.

Kaepernick has remained largely mum about the controversy since it erupted and has limited his public time off the field primarily to promoting charitable causes, including his foundation aimed at fighting oppression.

The NFL in recent years has shown itself to be forgiving in some areas but thus far has shown few signs of giving Kaepernick another chance. The Seahawks brought him in for a visit, the Baltimore Ravens were weighing adding him to the roster, and the Miami Dolphins might be considering their options after quarterback Ryan Tannehill suffered a leg injury Thursday in practice.

“I know a lot’s been written about it,” Dolphins owner Stephen Ross told reporters last week, “but you know owners and coaches — they’ll do anything it takes to win. If they think he can help them win, I’m sure — I would hope they would sign him.”

Still, he’s reportedly had zero offers, even though he has sent word that he intends to stand for the anthem this season. There have been more than a dozen other quarterbacks to sign free agency deals this offseason — Chase Daniel, Josh McCown and Geno Smith among them. With Joe Flacco temporarily sidelined with a back injury, the Ravens signed a quarterback named David Olson, a backup in college who threw all of three passes and spent last season in the Champions Indoor Football League. He also has dabbled in real estate.

Kaepernick, who has led his team to a Super Bowl, meanwhile, continues to wait.

Malcolm Jenkins, the Eagles safety who also took a knee during the anthem last year as a form of protest, on Thursday called owners “cowards” and said “it’s certain owners’ way of making an example out of [Kaepernick] to discourage anybody else from doing what he did.”

“That message, to me, is loud and clear from owners as to where their priorities stand and how they go about picking and choosing who they want on their teams,” Jenkins said, according to the Delaware News Journal. “It’s definitely unfortunate, but it’s shining a light on just how the NFL operates and what we deem as acceptable. It really has nothing to do with what’s right or wrong, but what affects dollars. That’s business as usual, but I think it’s an unfortunate precedent to set.”

It’s not clear whether the Ravens have shut the door on Kaepernick. Their backup, Ryan Mallett, has struggled in the early days of camp. ESPN reported Wednesday that Coach John Harbaugh and General Manager Ozzie Newsome were open to signing Kaepernick but met resistance from the team owner Steve Bisciotti. The Ravens issued a statement later in which Newsome said, “We are going through a process, and we have not made a decision. Steve Bisciotti has not told us we cannot sign Colin Kaepernick, nor has he blocked the move.”

The team has gauged the interest of fans and also retired linebacker Ray Lewis, who issued a rambling video on social media in which he implored Kaepernick to “let your play speak for itself. And what you do off the field, don’t let too many people know.”

That’s not a guiding philosophy in NBA circles. There are many reasons — NBA contracts offer more guarantees, for starters, and players might feel more job security — but star basketball players have taken the exact opposite tack in recent years.

“The NBA is such a global game,” Cuban said in an email, “I think our players exposure to different political systems among their teammates may help them appreciate our country even more and encourage their participation.”

Van Gundy said Silver has set a tone in which he feels “there are bigger things than basketball and the business of basketball.”

“And so players have shown that you can [be] both basketball businessmen and still retain your voice on issues that directly impact their communities,” he said. “I think that’s a great sign. It wasn’t too long ago where some thought that if they spoke out on issues, it might impact their brand.”

If anything, being outspoken or socially aware has become a part of some players’ brands. The NBA has shown itself to be particularly progressive on social issues. In 2013, Jason Collins became the first male athlete from a major American sport to come out as gay. In 2012, LeBron James and his Miami Heat teammates wore hoodies during warmups to honor Trayvon Martin. In 2014, Silver issued a lifetime ban of former Clippers owner Donald Sterling after he was recorded saying racist remarks.

Across the board, they have been more outspoken than their counterparts from other sports on topics ranging from Black Lives Matter to Donald Trump’s presidency. Coaches such as Gregg Popovich, Stan Van Gundy and Steve Kerr have talked politics, and big stars such as James, Stephen Curry, Carmelo Anthony and Derrick Rose have used their platform to discuss gun violence and social activism. In 2015, with the league’s support, filmmaker Spike Lee produced a public-service announcement featuring NBA stars that aired during its Christmas Day telecasts.

“The NBA has always led,” Lee told The Washington Post last year. “It’s hipper and more progressive than other professional sports. I’m not trying to slam anybody; it’s just my opinion.”