By Lily Jamali

SAN FRANCISCO (Reuters) - He may be on the second-string roster of the San Francisco 49ers, but all eyes will be on backup quarterback Colin Kaepernick when the national anthem plays for the team's first Monday night football game of the season, at home against the Los Angeles Rams.

Kaepernick has ignited a National Football League controversy by refusing to stand during "The Star-Spangled Banner" at the start of the team's preseason games to protest what he has called racial injustice and police brutality.

The gesture by Kaepernick, who is African-American, has been imitated by numerous other NFL players in recent days.

On Sunday, Kansas City Chiefs cornerback Marcus Peters, also black, raised his fist during the national anthem for his team's home-game season opener against the San Diego Chargers.

His action recalled the raised-fist salute by black athletes Tommie Smith and John Carlos during their medal ceremony at the 1968 Olympic Games in Mexico City. Carlos, now 71, praised Kaepernick, Peters and other NFL players in a Reuters interview on Monday for using their televised platforms as professional athletes to give Americans a "shock treatment."

Other members of the Chiefs linked arms during Sunday's anthem, as did the Seattle Seahawks at their home game against the Miami Dolphins. The exact meaning of their gestures was not clear.

Four members of the Dolphins knelt while the "Star-Spangled Banner" played on Sunday. In Thursday's NFL season opener, Denver Broncos linebacker Brandon Marshall had knelt during the anthem.

The protesting players have been seen as allies of the Black Lives Matter movement, which grew in response to a string of high-profile police killings of unarmed black people across the country. About two-thirds of NFL players are black.

The protests also have provoked anger in some fans who see the gesture as disrespectful to the U.S. flag, the military and the nation in general.

President Barack Obama has weighed in on the controversy, saying Kaepernick was exercising a constitutional right and provoking conversation "around some topics that need to be talked about."

Monday's matchup in San Francisco between the Rams and the 49ers will turn the spotlight again on Kaepernick at the start of one of two NFL games ESPN is featuring for its opening-week of the popular "Monday Night Football" broadcasts.

The California-based group supporting Kaepernick, the Courage Campaign, said it plans to fly a plane over the 49ers' Levi's Stadium just before Monday night's game with a banner that will read: CourageCampaign: Kap Inspires Courage!"

Earlier in the evening, the Washington Redskins hosted the Pittsburgh Steelers in a game that opened with players from both teams joining U.S. military personnel to hold up a giant American flag as it was unfurled over the field while the national anthem played. No signs of protest were immediately evident from the broadcast.

(Reporting by Steve Gorman in Los Angeles; Additional reporting by Curtis Skinner in San Francisco; Editing by Mary Milliken and Cynthia Osterman)