Colin Kaepernick will sue NFL owners for not hiring him after he kicked off the controversial practice of kneeling for the national anthem, reports claim.

'I am told that @Kaepernick7 has filed a grievance under the CBA for collusion against the owners. If accurate, this is huge,' Bleacher Report's Mike Freeman wrote on Twitter.

Kaepernick, 29, has retained Mark Geragos, who has represented Michael Jackson, Chris Brown and Winona Ryder, among others, and is expected to release a statement soon.

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Colin Kaepatrick (left and right), who ended his contract with the 49ers in March, has not been picked up by any other teams. He's now filing a collusion suit against NFL owners

Many members of the San Francisco 49ers are seen kneeling on October 8. Kaepatrick began the practice, which was then taken up by several other teams' players - causing much anger

It's now been reported that Kaepatrick, believing that his lack of a hire is down to collusion, is filing a grievance under the NFL's Collective Bargaining Agreement (CBA)

He has reportedly hired lawyer Mark Geragos. NFL Commissioner Roger Goodell has denied any kind of blackballing towards Kaepatrick

It's not yet clear who exactly the quarterback - who kicked off the controversial practice at kneeling for the national anthem in protest at police violence on black men - intends to sue.

But given that he's now gone six weeks of the latest season without backing, despite playing well last season, his annoyance may not be unwarranted.

Kaepernick opted out of his 49ers contract in March, likely expecting a warm welcome to another team.

Geragos (pictured) has represented Michael Jackson, Chris Brown and Winona Ryder, among others

And having scored 16 touchdowns and only four interceptions in 12 games last season, a warm welcome wasn't out of the question.

Instead, he's found himself sitting around waiting to be hired - without luck, something he apparently attributes to collusion by the NFL teams.

'Collusion occurs when two or more teams, or the league and at least one team, join to deprive a player of a contractually earned right,' Sports Illustrated explained.

'Such a right is normally found in the collective bargaining agreement [CBA] signed by a league and its players’ association.

'For example, the right of a free-agent player to negotiate a contract with a team cannot be impaired by a conspiracy of teams to deny that a player a chance to sign.'

NFL commissioner Roger Goodell told ESPN last year that Kaepernick was not the subject of any kind of team collusion.

He said that all teams will 'do whatever it takes to make their football team better. So those are football decisions. They're made all the time.

'I believe that if a football team feels that Colin Kaepernick, or any other player, is going to improve that team, they're going to do it.'

However, the movement start by Kaepernick has continued to prove controversial, and has lead to many fans threatening to boycott teams and players.

On Tuesday, Goodell sent a memo to players warning them that 'that everyone should stand for the National Anthem,' and adding that the league needs to 'move past' the controversy surrounding player protests.

President Trump has seized on the controversy, which has energized his fanbase.

Last week president Donald Trump said that the NFL should have suspended quarterback Colin Kaepernick the first time he kneeled for the National Anthem

In March he told a rally in Kentucky that 'NFL owners 'don't wanna pick [Kaepernick] up because they don't wanna get a nasty tweet from Donald Trump.

'Do you believe that?' he asked the cheering crowd. 'I said I'm gonna report that to the people of Kentucky, because they actually like it when people stand for the American flag,' he said.

And on Wednesday he told Fox News' Sean Hannity: 'The NFL should have suspended [Kaepernick] for one game and he would never have done it again.

'They could have then suspended him for two games and they could have suspended him again if he did it a third time, for the season, and you would never have had a problem.'