Detroit heads into Thursday Night Football with a dangerously thin defensive backfield.

The Lions officially placed Terrion Arnold on injured reserve, ending the second-year corner’s season as he prepares for shoulder surgery. The injury has lingered ever since Week 5 against the Bengals, affecting both Arnold and the Lions’ defense, so the decision to shut him down was long overdue.

But losing Arnold — on top of Kerby Joseph likely being done for the year — leaves Detroit’s secondary badly depleted and highly vulnerable against the pass. With the Lions needing a Week 14 win to keep their playoff hopes afloat, the timing could hardly be worse, especially with CeeDee Lamb and George Pickens waiting on the other side.

A defensive backfield once viewed as a strength has been reduced to its thinnest state with only five games left.

Detroit’s Options vs. Lamb and Pickens Look Slim

Here are the cornerbacks the Lions currently have available for Thursday’s home matchup:

Rock Ya-Sin

D.J. Reed

Khalil Dorsey

If needed, Detroit can also turn to Amik Robertson or Avonte Maddox. At safety, the Lions have:

Brian Branch

Daniel Thomas

Thomas Harper

And that’s the full group. Branch has performed well since returning from injury and suspension, but he doesn’t bring the ball-hawking presence Joseph provided in recent seasons. Reed is back just as Arnold goes down for good, stopping that free-agency experiment before it ever fully took off.

It’s unrealistic to expect the remaining depth pieces — Harper, Thomas, Maddox, or Robertson — to suddenly play at the level of Detroit’s injured stars. Yet that’s essentially what defensive coordinator Kelvin Sheppard needs if the Lions hope to survive what is arguably one of the few NFC matchups left on their schedule that they should be competitive in.

Meanwhile, Dallas enters the game riding a three-win streak, and with the NFC tightening up, the Cowboys remain firmly in the postseason race as long as they keep winning.

That puts immense pressure on Lamb and Pickens to continue delivering explosive plays. Considering how Detroit struggled to contain Jordan Love’s deep passing on Thanksgiving, it’s difficult to picture the Lions fixing their coverage issues in such a short turnaround.

A victory would increase Detroit’s playoff odds to 45 percent. A loss would send them crashing to 12 percent — nearly ending their hopes altogether.