MINNEAPOLIS -- NFL commissioner Roger Goodell encouraged players to speak their minds on social issues Sunday in the wake of Colin Kaepernick's decision not to stand for the national anthem.

While Goodell said he has not reached out to the San Francisco 49ers quarterback, he praised the shift of players' activism from "protests to progress."

"As I've said before, I truly respect our players wanting to speak out and change the community," Goodell said at U.S. Bank Stadium before Sunday night's game between the Minnesota Vikings and Green Bay Packers. "We don't live in a perfect society. We want them to use that voice. They're moving from protests to progress and trying to make things happen in the communities, and I admire that about our players [being] willing to do that."

Kaepernick, who initially said he was sitting during the anthem to raise awareness about the treatment of African-Americans in the U.S., knelt again before the 49ers' game Sunday against the Carolina Panthers. Players around the league have followed the quarterback's lead in a number of different forms, whether kneeling during the anthem or locking arms as a team, like the Seattle Seahawks did before their season opener Sept. 11.

"Obviously, we want to respect people," Goodell said. "We want to respect our differences. We want to reflect our flag and our country, and our players understand that. So I think where they're moving and how they're moving there is very productive, and we're going to encourage that."