President Donald Trump, whose controversial remarks Friday inspired an outpouring of protests before NFL games Sunday, once again took aim at those kneeling during the national anthem.

There were some unprecedented moments during pre-game ceremonies before Sunday's games. 

All of the Pittsburgh Steelers, with the exception of lineman Alejandro Villanueva, a U.S. Army veteran and Bronze Star recipient, stayed in the locker room during the national anthem at Soldier Field. 

Several NFL owners joined their players on the field in a show of support.

The president, who earlier on Sunday had tweeted that fans should boycott the NFL if the league did not crack down on national anthem protests, apparently liked some of what he saw Sunday, specifically the players standing in solidarity.

The president tweeted: "Great solidarity for our National Anthem and for our Country. Standing with locked arms is good, kneeling is not acceptable. Bad ratings!"