The Lions Defense is actually still pretty good. Statistically, it's just brought down immensely by their passing yards defense

Season defensive stats:
Third Down defense: 32.4% (1st)
Red Zone defense: 50.9% (7th)
Rush Defense Yards Allowed: 98.4 (5th)
Pass Defense TDs Allowed: 18 (2nd)
Scoring Defense TDs Allowed: 37 (7th)

The rushing defense has been good even post injuries. A lot of these numbers are still good actually. Basically the fatal flaw for our defense is we let way too many yards through the air. The Eagles, somehow, have an awful passing offense (4th worst in the game by yardage, and not amazing by scoring). Commanders, however, are 7th best in this regard.

The one thing to worry about though is that Detroit plays an insane amount of man coverage, and Jalen Hurts is really good against man coverage. On the other hand, Goff is pretty good against Zone, but most of his picks come from zone coverage, which the Eagles defense use very frequently.