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.

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."

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.