So this week has been a refresher.
Detroit nickel back Bill Bentley hasn't practiced all week. The chances of him playing against Chicago are minimal at best. So the Lions, who have had to shift their cornerbacks and nickel often this year due to injuries (Mathis) and benchings (Chris Houston and Darius Slay), will have to be on the move again.
At least this time they had some time to practice with their actual plan.
"We can do it a lot of different ways," Detroit coach Jim Schwartz said. "Mathis gives us flexibility. In the last game against Dallas, we had a package where Don Carey played in there also. He has the flexibility to be able to do that.
"Both of our safeties can cover wide receivers, so we don't necessarily have to go nickel. Both of those guys have good range and good man-to-man skills and former corners in their background. We'll have a lot of different ways to be able to handle that."
The most likely option, though, will be seeing Mathis move inside and rookie Darius Slay, who started the first two games of the season before being benched and then consistently brought in when players are injured, out to the corner opposite Chris Houston.
Mathis, a former All-Pro at corner, feels "very comfortable" if he had to move inside.
"If we definitely had an issue at nickel, I'd go in," Mathis said. "I have the tools in my tool belt. I had to knock off a little rust, but I still possess it."
Practice this week, he said, helped. And the major difference in being outside on the corner versus inside at the nickel on slot receivers actually fits him better because of his familiarity with the defense.
"Just playing a little more in space. The receivers have a little more space to work with so you have to, they have two-way gos," Mathis said. "Sometimes at corner, when you're out there on the outside, their alignment dictates whether they are going inside or outside. In the nickel, you never know.
"You have to be solid and a little more patient, patient in the nickel than on the outside. I think I possess a little patience."
Detroit is able to do this because of a renewed confidence in Slay, who has played decently when he has been forced into games since he lost his starting job following the second week of the season.
Being able to watch and then play, watch and then play has actually helped him progress.
"I got so used to the speed now, I'm not second guessing what's going on," Slay said. "I know a lot of folks done seen it on film, that I'm improving every week."
He has, although defensive coordinator Gunther Cunningham was still bothered by a couple of plays Slay didn't make -- or misread -- against Dallas. He is, after all, still a rookie.
Whatever happens Sunday against Chicago, for the first time this season, Detroit is actually prepared beforehand rather than having to adjust in the middle of a game.