Weak Link Systems in the NFL: Why Ragnowrok will hit the Detroit Lions’ offense

Detroit is a solid bet to underperform expectations this year. Let’s learn about “Weak Link” systems.

The Green Bay Packers play in a very difficult division. At least, the NFC North was a very difficult division last year, and it will probably be pretty good in 2025, but there are some question marks that have started to pop up. The Vikings are making a major change at quarterback and, of course, the Bears are counting on Ben Johnson to resurrect quarterback Caleb Williams, because that is what the Bears do.

You don’t hear too much about the Lions, however, and I would like to talk about the Lions because I think there’s a strong case to be made that they fall off of a cliff. At least a bit — keep in mind that they won 15 games last season, and so they’re standing on a pretty high cliff.

When forecasting NFL teams, the most important single concept to understand is likely the “weak link system.” While things like fumble luck and injuries will be major factors for any team, they don’t really reflect any information about the underlying talent or roster construction. We can, to some small extent, project how lucky or unlucky a team will be compared to last year and that’s useful, but it’s not really information about the team.

When I make projections, aside from the above “luck” factors, I also take a long look at defensive performance in general. Offensive performance tends to be more stable from year to year (more on this in a second), but defensive performance fluctuates wildly, for two main reasons:

1. The defense does not control the ball, and so the agency of the defense is fundamentally limited. The difference between a good defense and an average defense can be as simple as the number of times each faces some combination of Patrick Mahomes, Josh Allen, Lamar Jackson, and Joe Burrow.
2. NFL defenses are a weak link system, meaning their overall production is much more susceptible to changes in personnel than is the case on the offense.

Think of it this way: If your number two receiver gets hurt, you have several options to compensate. You can ask more of your number one and divert targets to him. You can run the ball more or use more 12 personnel to get an extra tight end on the field instead of an extra receiver. It’s not as if the injury won’t do ANY damage at all, but since you control the ball, you get to dictate how you solve this problem.

On the defensive side though, it’s a completely different story. If your number two cornerback is injured, you CANNOT ask more of your number one corner. As most NFL defenses run nickel as a base with two outside corners and a slot specialist on the field, you are either forced to move your slot/nickel corner outside and bring in a bench player to cover the slot or bring in...