For his first start in almost a year, the San Francisco 49ers quarterback showed up in a T-shirt with a photo of Muhammad Ali on the front. Before the game, he knelt on one knee for the pregame national anthem.
The Buffalo Bills fans had their replies ready.
Before the anthem, the crowd chanted "USA! USA!" When Kaepernick jogged onto New Era Field in Orchard Park, New York, for his first snap, the crowd greeted him with boos -- and not just because he played for the Bills' opponent.
Such is the life of a lightning rod.
In the end, Kaepernick and his teammates were crushed 45-16 in a game that was about something besides football.
Kaepernick is one of the most famous athletes in the United States. Time magazine put him on the cover. Kaepernick's No. 7 jersey has become the NFL's top seller
It's all because during the 2016 preseason he began sitting -- then later kneeling -- during the US national anthem, saying he didn't want to "show pride in a flag for a country that oppresses black people and people of color."
His protest thrust the Black Lives Matter movement, which has mobilized nationwide protests and other civil actions against alleged police mistreatment of African-Americans, firmly into the NFL and started a national debate.
Was Kaepernick insulting Old Glory or -- by taking a knee -- using his First Amendment rights to stand up for the black community?
It was a lot of attention for someone who wasn't doing so great on the field. Once a hero for leading the 49ers to a Super Bowl, Kaepernick had been relegated to a bench warmer this season.
That changed Sunday. After weeks of watching quarterback Blaine Gabbert struggle, coach Charles "Chip" Kelly called on Kaepernick to start against the Bills.
'Needs to show respect'
The Buffalo fans -- pro and con -- were ready
A guy sold T-shirts outside the stadium with a photo of Kaepernick in a rifle scope's crosshairs, the New York Post reported
. Somebody created a Kaepernick tackling dummy that fans took turns plowing into, the Post said.
"When Colin Kaepernick comes in to our house, he needs to show respect," C.J. Zimmerman told CNN affiliate WIVB
. He led a movement for fans inside the stadium to sing the national anthem.
But not everybody was against Kaepernick. A group called Just Resisting gathered outside the stadium and took a knee when the national anthem was played to show their support of Kaepernick, WIVB reported. "Stand up against racism," one of their signs said.
Kaepernick could have used some help on the field. He completed 13 of 29 passes for one touchdown and ran eight times for 66 yards in the loss. The 49ers, now 1-5, certainly hoped for more from the star.
Of course, Kaepernick hasn't started a game since November 1, 2015. Last season he had a 2-6 record as a starter under former coach Jim Tomsula before being benched in favor of Gabbert. Kaepernick was later placed on season-ending injured reserve with a left shoulder injury.
Criticized by Trump
He's not the first athlete to call attention to racial injustice. In fact, American Olympians John Carlos and Tommie Smith famously raised their fists in a black power salute at the Summer Olympics on October 16, 1968
-- 48 years ago.
Kaepernick, who is biracial, started kneeling during the national anthem in preseason games to raise awareness about racial issues. Death threats poured in.
"It's to protest the injustices that are happening in America, the oppression that is happening in America, and these things need to be addressed on many different levels," Kaepernick said.
Then other athletes -- from elementary schools to professional sports teams -- began following his lead. Because it's a political year, his stance became enmeshed in politics.
Donald Trump bashed him. President Obama supported him. Supreme Court Justice Ruth Bader Ginsburg said his protest was "really dumb," then backed off her statement.
Kaepernick has not wilted under the attention. He sounded off a time or two himself, as when he called Trump and Democratic candidate Hillary Clinton "proven liars."
To people who say he's unpatriotic, Kaepernick replies: "I'm not anti-America. I love America. I love people. That's why I'm doing this. I want to help make America better."
But this is pro football. Can he make the 49ers better?
That question may be answered next week when San Francisco plays the Tampa Bay Buccaneers at home.