What began as a quiet protest against police brutality and racial inequality catapulted Colin Kaepernick to the forefront of the "Black Lives Matter" movement.
It also left the former San Francisco 49ers quarterback without a job, a pariah in the National Football League (NFL).
Two years after sitting on the sidelines during the playing of the national anthem, the 30-year-old athlete has become one of the most controversial figures on the US landscape.
As a mobile quarterback with a rifle arm, Kaepernick took the 49ers to the Super Bowl in 2012 and to the NFC championship game the following season.
Seen as the quarterback of the future, the heir to legends Joe Montana and Steve Young, he signed a six-year contract extension with the 49ers in June 2014 paying him up to $126 million, with $61 million guaranteed.
Kaepernick lost his starting job in 2015 but was battling to regain it at the dawn of the 2016 season.
He staged his first silent protest during the team's third preseason game, sitting on the bench and declining to join his teammates during the traditional playing of "The Star-Spangled Banner."
"I am not going to stand up to show pride in a flag for a country that oppresses black people and people of color," Kaepernick told reporters after the game. "To me, this is bigger than football and it would be selfish on my part to look the other way."
Referring to the recent high-profile slayings of several young black men by police officers, Kaepernick said: "There are bodies in the street and people getting paid leave and getting away with murder."
For the next preseason game, he was persuaded by a former NFL player and serviceman to kneel instead of sit.
The kneeling protest was adopted by several other black players and in September 2017 it drew the attention of President Donald Trump, who declared that NFL owners should fire any "son of a bitch" who failed to stand for the anthem.
The protests have left NFL fans divided with some claiming that they are disrespectful to veterans and the flag and others demanding that the league support players exercising their free speech rights.
- Grievance against the NFL -
Kaepernick asked the 49ers to be traded in 2017 and he has been unable to find an NFL job since then, filing a grievance against team owners who he accuses of colluding to keep him out of the league.
That lawsuit is ongoing.
Since his effective banishment by the NFL, Kaepernick has embraced the role of civil rights activist in the mold of pioneering black baseball player Jackie Robinson and boxer Muhammad Ali before him.
He has donated money to groups fighting racial injustice and was named an "Ambassador of Conscience" by Amnesty International in 2018.
Kaepernick was born on November 3, 1987 to a teenaged mother who was white and a father who was black.
Put up for adoption, he was raised in California by a white couple, Rick and Teresa Kaepernick.
An outstanding all-around athlete -- the 6ft 4in (1.93-meter, 104-kilogram) Kaepernick played baseball and basketball in addition to football in high school.
A pitcher, he was drafted by Major League Baseball's Chicago Cubs in 2009 but decided to attend the University of Nevada in Reno instead to play college football.
After a standout college career, he was selected by the San Francisco 49ers in the second round of the 2011 NFL draft. He was the 36th player selected overall.
A backup his first year, Kaepernick took over as the 49ers starting quarterback in the 10th game of the 2012 season, taking them to the Super Bowl where they lost 34-31 to the Baltimore Ravens.
Kaepernick, who is deeply religious and sports several tattoos of Bible verses, led the 49ers to the NFC championship game the following year where they lost to the evetual Super Bowl champion Seattle Seahawks.
On Monday, shoe and athletic apparel giant Nike named Kaepernick as the face of a new advertising campaign to mark the 30th anniversary of the company's iconic "Just Do It" slogan.
The Nike campaign, unveiled just days before the kickoff of the 2018 NFL season on Thursday, shows a portrait of Kaepernick with the slogan: "Believe in something. Even if it means sacrificing everything."
"We believe Colin is one of the most inspirational athletes of this generation, who has leveraged the power of sport to help move the world forward," said Gino Fisanotti, Nike's vice president of brand for North America.
The campaign has sparked a backlash among some fans with a #NikeBoycott hashtag trending on Twitter while others have come out in support of the company and the ostracised quarterback.