Jeremy Fowler of ESPN.com reported the news, calling the decision "a sign of solidarity."
According to Fowler, some of the coaches—including head coach Mike Tomlin—were on the sideline, but the players didn't come out until after the anthem ended.
Fowler noted left tackle Alejandro Villanueva, who previously served in Afghanistan, had his hand on his heart during Sunday's anthem:
"You know, these are very divisive times for our country and for us as a football team it's about us remaining solid,” Tomlin told CBS Sports' Jamie Erdahl, via Ryan Wilson of CBS Sports. "We're not going to be divided by anything said by anyone. ... "[I told our players] if you feel the need to do anything I'm going to be supportive of that -- as Americans you have that right. But whatever we do we're going to do 100 percent, we're going to do together. We're not going to let divisive times or divisive individuals affect our agenda."
The Steelers' actions come after President Donald Trump turned heads during a rally in Alabama on Friday by referencing NFL players who protest racial injustice and police brutality by kneeling during the national anthem.
Bryan Armen Graham of the Guardian shared Trump's comments, including the notable one where he said NFL owners should "get that son of a bitch off the field right now" if a player kneels during the anthem:
NFL Commissioner Roger Goodell issued a statement following Trump's bombastic take:
The NFL and our players are at our best when we help create a sense of unity in our country and our culture. There is no better example than the amazing response from our clubs and players to the terrible natural disasters we've experienced over the last month. Divisive comments like these demonstrate an unfortunate lack of respect for the NFL, our great game and all of our players, and a failure to understand the overwhelming force for good our clubs and players represent in our communities.
Steelers president Art Rooney II said Saturday, "I believe the commissioner made an appropriate statement and I have nothing to add at this time," per Ed Bouchette of the Pittsburgh Post-Gazette.
Trump wasn't done with the NFL on Sunday morning, again taking to Twitter to express his displeasure:
A number of professional athletes and NFL teams have criticized Trump for his comments, as Miranda Green of CNN noted.