The Cowboys Are Already Rebuilding Their Defense Around Injuries. What Does NFL Depth Really Mean?

On the final play of Dallas's 34-31 loss to Baltimore in Rio de Janeiro, the Cowboys had four backups on the field. That's Week 3.

Now Dallas heads into Sunday's game against the Houston Texans with six players on injured reserve with a designation to return, and two more defensive starters headed there. My argument is that depth in the NFL isn't a number on a roster. It's how much of your system survives when the people who know it aren't available.

The list keeps growing

The Cowboys placed safety Jalen Thompson, the team's biggest free agent signing, and defensive tackle Jonathan Bullard on injured reserve on Wednesday. Both were hurt against the Ravens. They're eligible to return after four games, which means they'll miss a month.

They join a list that includes safety P.J. Locke, who tore a plantar fascia in the Week 2 win over Washington. The team's injury report also names players like Cobie Durant and Shavon Revel Jr. as dealing with issues at cornerback, though both appear to have avoided injured reserve.

The Dallas Morning News reported that through three weeks, the Cowboys had only two of the five secondary starters they began the season with. Yahoo Sports counted 29 different players who've taken defensive snaps. For comparison, that's well over the 11 you need on the field at any moment.

Depth isn't just replacement bodies

That's where I think people misread the word. Teams talk about depth as if any competent player can slot in. In practice, a defense is a set of agreements. Safeties and corners have to know who covers what when the formation shifts, and those agreements take weeks to learn.

Head coach Brian Schottenheimer said as much, acknowledging the Cowboys may play with some players who don't have a deep understanding of the scheme. His solution is to simplify. The plan isn't to fool the Texans. It's to execute a smaller menu of calls well.

This is a cost of depth that doesn't show up on the injury report. A defense with all 11 starters can run a complicated game plan. A defense with a patchwork secondary has to trim the plan, and that gives an offense an easier read.

The roster fixes

Dallas has responded by adding defensive linemen and defensive backs, while also working out veteran linebacker Germaine Pratt, who has 104 career starts.

Safety Malik Hooker returned to a light practice, which helps. If he can't go, the team will likely lean on Markquese Bell and Alijah Clark, the same pair that filled in against the Ravens.

Why the schedule makes it harder

The calendar isn't helping. The Texans game is Sunday, and a Thursday home game against the Tampa Bay Buccaneers follows in Week 5. That leaves little time for a new safety to learn the defense or for an injured player to heal.

There's a decent argument that this is the part of football fans never see. Depth gets decided in the spring, when general managers choose how to spread their money, and in training camp, when backups learn the system. By Week 4, the choices are made.

So here's the question for the front office. When you build a roster, is it smarter to spend on a few high-end starters and hope they stay healthy, or to spread resources so that a bad Sunday doesn't force you to rewrite your defense?

Editor's note: Dallas plays the Texans on Sunday, October 4. This was written before any results.