Multiple Cleveland Browns players kneeled during the national anthem before the team's game against the Colts on Tuesday as the field was covered by a giant American flag.
A handful of Colts players also kneeled during the anthem, including Al Woods, Malik Hooker, Kamar Aiken and Rashaan Melvin.
Colts fans reportedly booed the players that did, and Browns fans who support Trump brought a sign to the stadium.
On Friday night, president Donald Trump said NFL owners should "fire" NFL players who protest the anthem and referred to them as "son of a b----." His comments have been criticized by multiple NFL owners, players and the commissioner. Players have responded with a number of different protests and signs of solidarity; most teams have linked arms during the anthem, while a number of players kneeled.
The Pittsburgh Steelers opted to stay in the locker room during the anthem.