Kansas City cornerback Marcus Peters raised a black-gloved fist during the national anthem before the NFL opener against San Diego, backing up his promise to show support for protests started by Colin Kaepernick.

It was the only such gesture visible throughout the early games Sunday, as the anthems took on more significance because of the 15th anniversary of Sept. 11 attacks. The Seattle Seahawks said last week they planned a demonstration of “unity” when their game against Miami kicks off Sunday afternoon.

Several teams, including the Chiefs, saw their players link arms during the anthem. Peters, the 2015 Defensive Rookie of the Year, was the last person in the Chiefs’ line and had his arm free to raise it.

Marcus Peters of the Chiefs, raising his fist during anthem. Dissent - especially in this NFL climate, - is brave. pic.twitter.com/VaGNS5pD45 — Dave Zirin (@EdgeofSports) September 11, 2016

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Peters said he was “100 percent behind” Kaepernick, who chose to sit and take a knee during the anthem in preseason games to call attention to what he termed the oppression of blacks and other minorities.

“He spoke up about something he felt he needed to speak up about,” Peters said. “I salute him for that.”

Broncos linebacker Brandon Marshall , a teammate of Kaepernick’s in college at Nevada, took a knee during the anthem on Thursday night.

Peters’ gesture was also a tribute of sorts to U.S. sprinters Tommie Smith and John Carlos, who won the gold and bronze medals, respectively, in the 200-meter race at the 1968 Olympics. Both then appeared on the medal stands with raised, black-gloved fists throughout the U.S. national anthem in what they called a “human rights salute.”

The International Olympic Committee ordered Smith and Carlos expelled from the games because of the protest.

Meanwhile, athletes at the University of Texas have been urged to stand during the national anthem and not follow in the footsteps of Kaepernick.

In a memo sent three days after Kaepernick’s initial demonstration to school presidents and athletic directors through the state’s university system, University of Texas System Chancellor William McRaven wrote:

“I spent 37 years defending freedom of speech and freedom of expression. Nothing is more important to this democracy. Nothing! However, while no one should be compelled to stand, they should recognize that by sitting in protest to the flag they are disrespecting everyone who sacrificed to make this country what it is today – as imperfect as it might be.”

McRaven rose to the rank of admiral in the U.S. Navy and most notably organized and oversaw the missionto kill Osama bin Laden in May 2011 as the commander of the Joint Special Operations Command. Later that year, he was given command of the entire U.S. Special Operations Command, a post he held until his retirement from the military in 2014, after which he was appointed chancellor of the university.

For McRaven, the protests are misplaced.

Kaepernick protest analysis

“Those that believe the flag represents oppression should remember all the Americans who fought to eliminate bigotry, racism, sexism, imperialism, communism, and terrorism,” the McRaven memo stated. “The flag rode with the Buffalo Soldiers of the 9th, 10th, 24th and 25th Cavalry and Infantry regiments. It was carried by the suffragists down the streets of New York City. It flew with the Tuskegee Airman of WWII. IT was planted in the fields where Cesar Chavez spoke. It marched with Martin Luther King Jr. It rocketed into space on the shoulder patches of women, gays, Hispanic, Asian and African American astronauts. Today, it waves high over the White House. It is a flag for everyone, of every color, of every race, of every creed, and of every orientation, but the privilege of living under this flag does not come without cost. Nor should it come without respect.

“The nation and everything it strives for is embodied in the American Flag,” the McRaven memo continued. “We strive to be more inclusive. We strive to be more understanding. We strive to fix the problems that plague our society. But in striving to do so, we must have a common bond; some symbol that reminds us of our past struggles and propels us to a brighter, more enlightened future. That symbol is the American flag.”

NFL Commissioner Roger Goodell also disagrees with Kaepernick’s choice to kneel during the national anthem, but recognizes the quarterback’s right to protest.

Supporting Colin Kaepernick

Asked by The Associated Press about Kaepernick’s decision not to stand before games when the national anthem is played, Goodell said in an email Wednesday: “I don’t necessarily agree with what he is doing.”

“I support our players when they want to see change in society, and we don’t live in a perfect society,” Goodell added. “On the other hand, we believe very strongly in patriotism in the NFL. I personally believe very strongly in that.”

Goodell added that NFL players have a visible platform for their viewpoints. With that comes responsibility to use those platforms properly.

“We have to choose respectful ways of doing that so that we can achieve the outcomes we ultimately want and do it with the values and ideals that make our country great,” said Goodell, whose late father, Charles, was a U.S. senator.

“I think it’s important to have respect for our country, for our flag, for the people who make our country better; for law enforcement; and for our military who are out fighting for our freedoms and our ideals.”