In offices and workplaces across America, Friday is an unofficial day for downshifting—for dressing on the casual side and letting the mind wander to the weekend in store.

But there’s no place for “casual Fridays” in the NFL, at least not on teams that expect to make the playoffs. And that’s the alarm that Washington Redskins safety D.J. Swearinger has been sounding in recent weeks, troubled by what he describes as a lack of focus in the final full practice before game day.

In his view, it cost the Redskins in last week’s loss to the Minnesota Vikings. On a day when Washington’s offense scored 30 points (and should have scored more), its defense turned in its worst performance of the season, allowing Vikings backup quarterback Case Keenum to have a career day.

“Fridays have to be better here,” Swearinger said flatly in an interview this week, reflecting on the 38-30 defeat and the early-warning signs that, to him, pointed to a poor performance as clearly as a flashing neon sign.

“We didn’t practice as well as we should have Friday, and it ended up showing on Sunday,” Swearinger explained. “It was a good learning experience for us. I don’t think we’ll go back down that road again.”

Sunday’s game against the 7-2 New Orleans Saints, who are riding a seven-game winning streak, will tell a lot about whether Swearinger’s message is getting through.