The Eagles are terrible at stopping 3rd down plays (24th in the NFL by conversion percentage), and even worse on 3rd and long. On 3rd and 7 or 8, their percentage of failure actually rises to over 55%, vs. the low 40s for 1-6 yards. Even at 9-15 yards, the Birds give up first downs about 30% of the time.

What gives? There are some obvious conclusions: Philadelphia's run defense is better than its pass coverage. (In fact, it's one of the best in the league, as Reuben Frank documented.) The pass rush isn't getting home when it counts. No points for drawing those conclusions.

To some degree, this porousness is part of Chip Kelly's style of football, his much-discussed "bend but don't break" approach. Players are encouraged to gamble; sometimes Mychal Kendricks goes for the ball, allowing Matt Cassell to get 37 yards on a key 4th quarter pass to Chase Ford, but other times Kendricks or Brandon Boykin intercept.

One turnover can erase five 3rd-down conversions, and each takeaway has a disproportionate emotional effect on opponents, like the dunk in basketball. Sure, a dunk counts the same number of points as a layup, but....

The more talented your opponents are, the more valuable a gambling defense is

One key consideration heading into the playoffs: the more talented your opponents are, the more valuable a gambling defense is. When you face a Drew Brees who is likely to convert pass after pass, it makes sense to take some risks, as wunderkind Brent Cohen recently quantified. If you give up some yardage? Well, he was probably going to get those yards eventually, anyway. Now, whether your gamble works or not, you're dictating the game flow and getting your defense off the field quicker

The darker (and more fixable) reason for these lapses is pure defensive suckitude, specifically Philly's weakness at safety (especially when Earl Wolff is injured). Cornerbacks have to play off of their targets because if they miss a tackle, there may be no backstop (as Kendricks found out in that Vikings game; after he whiffed on the ball, Colt Anderson's failed tackle let Chase Ford get 24 YAC down to the Eagles' 5).

To get a deeper look at what's going on, I analyzed all 41 of the 3rd-and-long plays faced by the Eagles' defense since bye week (by my count, defining "long" as more than 5 yards). That's a big enough sample to draw some conclusions, while sticking with late season games gives credit to the major strides this defense has made. Four of these five games were against teams with winning records, so it's also a good preview for playoff football. (The fact that the only loss was against 3-9 Minnesota is a topic for another article.)

I looked at who defended on the play, where the throws went (center or wide, deep, short or screen), and whether the damage came on the throw or yards after catch. My gut impression off the top of my head was a lot of short to medium throws with big runs and broken tackles afterwards.

Overall, the Eagles' opponents converted 15 of 38 third-and-longs, or 39.5%. (The three fourth-and-longs where opponents didn't kick were even worse; they made 2 out of 3, including Kyle Orton's touchdown throw to Dez Bryant near the end of the Dallas game.) 35 of the 38 third-and-longs were run out of the shotgun.

If you think you know which defensive backs gave up the most plays, you're wrong. Brandon Boykin was covering on four failed stops, more than Patrick Chung's three, and Chung covered Jason Witten and Martellus Bennett very tightly on two of those.

Then again, Chung's third failure was the play where he laid out Boykin, freeing Larry Fitzgerald to run 26 yards after the catch for a TD. And muffed coverage by Chung against Detroit's Joique Bell would have given up another big first down, except for an ineligible receiver downfield penalty that bailed him out. Mychal Kendricks was also covering on four failed stops, one shared with Chung, and Cary Williams had two.

On the plus side, Boykin and Cary Williams stopped three plays each, but the stalwart was Connor Barwin, responsible all by himself for three of the stops and none of the failures.

The most surprising result, to me, was about the length of passes. (Opponents ran just four times out of 38 opportunities, and three of those failed; only Jay Cutler's 11-yard scramble just before halftime of the Bears game moved the chains.)

Contrary to my gut impression, yards after catch and short passes were not a big part of the problem. Only 5 of the 23 failed attempts were long throws, while there were 6 incompletes thrown for single-digit yards, most of them screens. Another 6 very short passes were caught but stopped short of the sticks.

Desperation seems to work best against the Eagles' defense

In contrast, the plays that burned the Birds were almost all double-digit throws. Only 3 plays involved significant yards after catch. One was a screen where Kendricks, Kurt Coleman and Demeco Ryans each missed a tackle that would have stopped Minnesota's Matt Asiata short of the first down; I urge you not to watch it if you value your low blood pressure. The other two were Kendricks' whiff and Chung's friendly fire on Boykin, which we've already discussed. Apparently the deep ugliness of these plays burned them into my memory in a way that gave them disproportionate weight.

What really seems to work best against Philadelphia is desperation. Minnesota succeeded because injuries to their two excellent running backs forced them to chuck it up, exposing the Eagles' greatest weakness. With little to lose, they threw their third-and-long desperation passes on all three downs and beat the Birds in a shootout (as did San Diego's Phillip Rivers). Another offseason should bring enough draft picks and free agents to patch up Philadelphia's secondary. In the meantime, let's pray for some nasty winter weather to discourage deep passing. Let it snow, let it snow, let it snow!

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