In one of the early games, one of the teams (except for one player, Alejandro Villanueva) remained in the locker room for the national anthem. In one of the late games, both teams will stay inside.
Via Albert Breer of TheMMQB.com, the Seahawks and Titans will stay inside for the playing of the Star-Spangled Banner.
The move could be problematic for the Steelers, Seahawks, and Titans. Said NFL spokesman Joe Lockhart via email: “Players are required to be on field for national anthem. Subject to fine if they are not. League has discretion on whether to fine them or not.”
It seems unlikely that the league would fine the players for staying inside, especially if (as in Pittsburgh’s case) the decision was made by the head coach. Also, any punishment imposed in connection with a team’s or a player’s handling of the anthem will invite intense criticism of the league, regardless of what the rules do or don’t say.