The NFL is reminding team personnel on the sidelines about the rules for wearing face coverings.
There were several games Sunday in which team members other than players were not using them.
There were times, in the game, Seahawks coach Pete Carroll had his mask off.
Troy Vincent oversees the league's football operations.
He sent a memo to the 32 clubs on Monday saying teams "must remain vigilant" about following protocols set not only by the league, union and clubs, but by state and local governments.
Otherwise, he says, the season could be "at risk."