Donovan McNabb wasn't the story

In this photo, Donovan McNabb is running, and the Eagles aren't stopping him. That was a big theme of Week 4. Getty Images

The Washington Redskins' 17-12 win over the Philadelphia Eagles on Sunday showed that Philadelphia is in serious trouble, and not just because of the injuries to Michael Vick, LeSean McCoy and others. The game showed that all their playmakers, even when healthy, may not have enough firepower to support one of the worst run defenses in football.

Conventional stats paint an interesting picture of the Eagles' run defense. While they rank 27th in rushing yards allowed per game (138.8), they've surrendered only 4.4 yards per carry, which is just barely higher than average. That suggests a mediocre run defense that has been tested over and over again, not a bad defense that can't stop anyone. However, in DVOA (defense-adjusted value over average, Football Outsiders' exclusive metric that analyzes every play of the NFL season and adjusts it for down, distance, score, field position, quality of opponent and other factors), the Eagles rank 29th.

Why so low?