J.J. Watt helps hold the flag with police officers and other first responders in Houston. (David J. Phillip/AP)

Across the NFL, as the first Sunday of the regular began with 11 games at 1 p.m., the focus was on patriotism and a solemn observance of the 15th anniversary of the Sept. 11 terrorist attacks on the United States.

In Seattle and Kansas City, though, there were a protest during the playing of the national anthem, something that became a possibility after San Francisco 49ers quarterback Colin Kaepernick began to protest police violence against minorities by remaining seated during preseason games.

At Seattle’s CenturyLink Field, the Miami Dolphins’ Arian Foster, Jelani Jenkins, Michael Thomas and Kenny Stills stood solemnly during the 9/11 ceremony, then knelt and placed a hand over their hearts during the playing of “The Star-Spangled Banner.” The Dolphins echoed NFL Commissioner Roger Goodell on the matter of protesting social causes.

The team, in a statement, said: “We encourage all members of our organization to stand at attention during the national anthem out of respect and appreciation for the freedoms we are afforded as Americans. We also recognize that it’s an individual’s right to reflect during the anthem in different ways. We respect these liberties and appreciate the sacrifices that everyone has made for our country, especially on this day of remembrance. We hope today’s events will continue a respectful and thoughtful dialogue in our community on unity inclusiveness and togetherness.”

Goodell urged players to be respectful and reminded them where they work.

“I support our players when they want to see change in society, and we don’t live in a perfect society,” he told the Associated Press last week. “We live in an imperfect society. On the other hand, we believe very strongly in patriotism in the NFL. I personally believe very strongly in that.”

On the other side of the field Sunday, the Seahawks linked arms in a display of unity, just as they had planned.

Wide receiver Doug Baldwin, whose father was a police officer and whose grandfather served in the military, acknowledged last week that keeping the message clear was important to the team as it considered what to do as a unit to show support during the 9/11 remembrance and for Kaepernick’s protest.

In a Facebook message, Baldwin explained what the Seahawks intend to do in a video, saying the team planned a show of unity. “We honor those who have fought for the freedom we cherish, and we stand to ensure the riches of freedom and the security of justice for all people. Progress can and will be made only if we stand together.”

In Kansas City, Chiefs players locked arms while cornerback Marcus Peters, at the end of the line of teammates, raised his free arm, holding aloft a fist throughout the anthem. “After having a number of thoughtful discussions as a group regarding our representation during the national anthem, we decided collectively to lock arms as a sign of solidarity,” the Chiefs said in a statement. “It was our goal to be unified as a team and to be respectful of everyone’s opinions, and the remembrance of 9/11.

“It’s our job as professional athletes to make a positive impact on our communities and to be proactive when change is needed. Together we are going to continue to have conversations, educate ourselves and others on social issues and work with local law enforcement officials and leaders to make an impact on the Kansas City community.”

For the most part, TV cameras came up with only patriotic displays as they scrutinized the sidelines. Players from the Green Bay Packers, Jacksonville Jaguars and Houston Texans helped hold the edges of the giant flags that are a staple of pregame ceremonies every week.

Some players, like the Tennessee Titans’ Avery Williamson and Atlanta Falcons’ Mohamed Sanu, risked fines for wearing shoes marking the date and failing to comply with NFL rules requiring that all players be dressed exactly the same.

“Never forget” was the message most players chose to convey, whether on T-shirts or shoes. The New York Giants’ Odell Beckham Jr. and Victor Cruz both opted to let their feet do the talking.

So did Tennessee’s Williamson.

Players wore red, white and blue decals in remembrance of the attacks on the back of their helmets and coaches wore 9/11 pins. In addition, recorded pregame messages from President Barack Obama and former President George W. Bush were part of the observance. Obama’s message was played before the 1 p.m. games and was to be shown again before the 4:05 p.m. EDT kickoff, Bush’s message before the 4:25 p.m. games. Messages from both men will precede the “Sunday Night” game between the New England Patriots and Arizona Cardinals.

Bush also did the coin toss preceding the Giants’ game against the Cowboys in Dallas and Vice President Joe Biden attended the Cleveland Browns game against the Eagles in Philadelphia. Biden, according to the White House, occupied the sidelines along with police officers, firefighters and emergency responders for the national anthem and a remembrance of victims of the attacks.

Jets wide receiver Eric Decker wore a Twin Towers T-shirt and NYPD cap during warmups. (Bill Kostroun/AP)

“Unity” was the theme of the day, whether with shows of patriotism or protest. Adam Jones of the Cincinnati Bengals chose not to protest saying that “there’s nowhere like America” and adding: “I understand we’re going through things as a country right now, but there’s just ways to do it. Me personally, I think when you do things, you have to do it in a unit. That’s my opinion on it and we’re ready to play football. We’ll be standing today for the national anthem today as a team.”