Manuel Balce Ceneta/Associated Press

President Donald Trump called on NFL players to recommend people for potential presidential pardons on Friday.

According to Pro Football Talk's Josh Alper, Trump said he would consider any cases in which players believe people were imprisoned incorrectly:

"I'm going to ask all of those people to recommend to me—because that's what they're protesting—people that they think were unfairly treated by the justice system. And I understand that. I'm going to ask them to recommend to me people that were unfairly treated and I'm gonna take a look at those applications and if I find and my committee finds that they've been unfairly treated then we'll pardon them. Or at least let them out."

Trump has vocally opposed NFL player protests against racial inequality and police brutality during the national anthem before games.

Last year, Trump caused an uproar among NFL players with comments at a political rally in Alabama: "Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say, 'Get that son of a b---h off the field right now. Out. He's fired! He's fired!'"

Despite that, the president acknowledged Friday that some NFL players have "seen a lot of abuse, [and] seen a lot of unfairness" during their lives.

In May, Trump pardoned late heavyweight boxing champion Jack Johnson, who was convicted of violating the Mann Act in 1913.

Johnson served 10 months in prison, but the morality of his conviction was long questioned due to the notion that it was racially motivated.

On Friday, Trump said he was also considering a posthumous pardon for boxing legend Muhammad Ali over his refusal to enter the Vietnam War draft in 1966.

While he has had issues with protests from NFL players, Trump likely won't have to worry about the issue over the course of the 2018 season.

In May, the NFL passed a new policy that will fine teams if players are determined to have disrespected the anthem or the flag.

Players will be permitted to remain in the locker room during the anthem if they so choose.