Donald Trump has often got involved in sports, whether it's presenting the World Cup trophy to Spain this summer or getting involved in WrestleMania.

The President of the United States doesn't shy away from giving his opinion and taking a stand against anything he opposes. That was no different in 2016, when his stance on a worldwide issue eventually cost an NFL player their career.

Trump even took credit for Colin Kaepernick being released, with the former quarterback never returning to the field to this day. Kaepernick, who represented the San Francisco 49ers for five years, has since become a controversial figure who splits opinion.

Colin Kaepernick Caused Outrage With NFL Protest

Back in 2016, Kaepernick was one of the biggest names in the sport, but he quickly became a figure of controversy. His refusal to stand during the American national anthem before games eventually led to his career ending.

Kaepernick would take the knee before matches instead, as part of the Black Lives Matter protests that were firmly in the spotlight at the time. That sparked booing from the stands and public outrage.

"I am often asked, 'Would you do it again?' And the answer is yes," he said about the protest in an interview with The San Francisco Standard. "Because of the impact I know it's had, the trajectory that has allowed myself and the organisations, other people in the communities, to be able to go out and do more, I don't think that can be overstated."

While he maintains he would do it all again, Kaepernick's actions were met with 'USA! USA!' chants and accusations of disrespecting the flag.

Donald Trump Wanted NFL Players Fired

Trump was also quick to get involved, declaring: "I think it’s a terrible thing. And maybe he should find a country that works better for him." The President later called for NFL players to be sacked if they knelt during the anthem.

At a rally in Alabama in 2017, Trump went on a foul-mouthed rant, saying: "Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say, 'Get that son of a b**** off the field right now, out, he's fired. He's fired!'.

"You know, some owner is going to do that. He's going to say, 'That guy that disrespects our flag, he's fired.' And that owner, they don't know it (but) they'll be the most popular person in this country."

Not stopping there, the businessman-turned-president even took pleasure in Kaepernick being unemployed that same year. "It was reported that NFL owners don't want to pick him up because they don't want to get a nasty tweet from Donald Trump," he told a crowd in Kentucky.

Kaepernick Blackballed From NFL After Kneeling

His protests and outspoken nature led to Kaepernick being without a club for a long time. It was reported that most NFL franchise owners were hesitant to sign him as he had become too political.

The backlash from Trump almost certainly played a role in his free agent status. Kaepernick ultimately never signed for another team after leaving the 49ers in 2016. He has since claimed that it has cost him more than $150 million in earnings, saying:

"It was costly. It cost me my football career that was 20-plus years in the making, something I loved dearly. And it cost me financially — $150-plus million, which is not a light load there. I think ultimately that where I want to see us as a society go, I don't think I would have been able to have the same impact or help put people in position in the way that I was able to if I didn't take that action."