Life used to be simple in a 3-4 defense. The fat guy was the nose tackle, the two other big guys were the defensive ends.

Today, the Cowboys find themselves in 4-3 defense, and things are getting a lot murkier weight-wise. Because it used to be that in a 4-3 defense you had two big guys who were the defensive tackles charged with plugging the middle, and you had two defensive ends who were a little more athletic than the tackles and were charged with rushing the passer. But with today's premium on pass rushing, everybody is tasked with rushing the passer, and the distinction between edge defender and interior defender is blurring. In Cowboys training camp this year for example, DEs Greg Hardy, Jeremy Mincey, Ben Gardner, and Ryan Russell have all taken turns playing inside.

Bill Parcells once explained that teams have certain criteria they look for at every position, because they know from experience that there is a certain combination of physical measurables that has proven successful in the NFL, and deviating from that success model doesn't have high chances of success.

Today, the heaviest defensive lineman on the Cowboys roster is Ken Bishop, who is listed a relatively svelte 305 pounds. By comparison, 11 of the 14 offensive lineman are heavier than that.

Are the Cowboys too light on their defensive line?

To find out, let's take a look at the weight of the starting defensive linemen on all fifteen 4-3 teams in the league. For this exercise, we'll use the depth charts at ourlads.com, which I've usually found to be pretty accurate, or as accurate as they can be in the preseason. The chart below summarizes the weight for each team.

The Giants have the heaviest projected defensive line with DE Cullen Jenkins (305 pounds), DT Markus Kuhn (299), DT Johnathan Hankins (320), and Jason Pierre-Paul (278). Nobody knows how the situation with Pierre-Paul will ultimately unfold, but if he doesn't return in time, rookie Owamagbe Odighizuwa (266) would likely take his place. In that case, the Giants would lose the top spot in our weight rankings to the Falcons, but still weigh in at a hefty 298 combined average weight.

In stark contrast, the Cowboys defensive line is by far the lightest defensive line in the league. Ourlads shows the Cowboys with a defensive line consisting of DeMarcus Lawrence (251), Nick Hayden (292), Tyrone Crawford (285), and Randy Gregory (235) for an average weight per player of just 266 pounds.

If I were to update those numbers with the current player weights as listed at Dallascowboys.com (251, 303, 285, 245), I'd get an average weight of 271, which would still rank the Cowboys last by a good 10 pounds per player. Even substituting Greg Hardy (279) for Randy Gregory and sticking with the DC.com weights would only give me an average weight of 280 pounds, still the lowest value in the league. Any way you slice it, the Cowboys will likely have the lightest defensive line in the league. Here's some more detail for each 4-3 team:

Weight of 4-3 defensive lines, 2015 (click column header to sort)

Team Total

D-Line Avg.

Defensive

Ends Avg.

Defensive

Tackles Avg.

LDE LDT RDT RDE NYG 301 292 310 305 299 320 278 ATL 299 271 328 260 310 345 281 DET 295 273 317 276 340 294 270 BUF 294 275 313 295 319 306 255 OAK 292 274 311 268 308 314 279 MIN 288 266 310 259 323 297 273 JAC 288 278 298 294 302 294 261 CAR 287 270 305 275 299 311 264 CIN 287 269 306 277 318 293 260 SEA 287 267 307 274 303 311 260 STL 287 271 304 276 285 322 265 NE 287 260 313 255 319 307 265 MIA 282 263 302 258 296 307 268 TB 282 263 301 260 295 307 265 DAL 266 243 289 251 292 285 235 NFL average 288 269 307 272 307 308 265

The 30 defensive ends in the table above average out at 269 pounds, and most people would probably consider that the ideal weight for a defensive end in a 4-3 defense. That's not saying that smaller (or larger) guys can't get the job done, but as Bill Parcells said, when you deviate from the success model you're facing longer odds to succeed.

We know that Randy Gregory continues to put on weight, and we also know that DeMarcus Lawrence weighs more than the official 251 pounds he's listed at. Nevertheless, both remain underweight relative to the NFL average. But that may not mean as much to the Cowboys, who believe that Gregory makes up for size with 'heavy hands' as Todd Archer of ESPN Dallas writes.

But just because Gregory is not the biggest doesn’t mean he can’t play big. Gregory has what scouts and coaches call "heavy hands." Gregory’s athleticism is his most impressive trait. On a one-on-one pass rush move against R.J. Dill on Sunday, he was able to bend so low around the corner, his hands dragged on the grass, which is something DeMarcus Ware perfected in becoming the franchise’s all-time leader in sacks. But what the heavy hands allows Gregory is the chance to battle much bigger offensive linemen if his speed and quickness doesn’t work. He can redirect them in a bid to get to the ball carrier or quarterback.

But it's not just the defensive ends that are a bit light. The Cowboys also have the lightest defensive tackle combo in the league. Even if I were to plug in the Cowboys' heaviest defensive tackle, Ken Bishop (305), next to Tyrone Crawford, the Cowboys' tackle duo would only weigh in at an average of 295 pounds, which would still be the lowest in the league.

However, overall weight may have been more important in the past than it is today. It used to be that especially the defensive tackles needed to stop the run, take on double teams and anchor to hold their ground. But today, a quality defensive tackle needs to be able to collapse the pocket and rush the passer. They can do this with brute strength and explosion to overpower their opponents or they can do it using their quickness - both lateral and vertical - to get off the snap and squeeze through gaps. What they can't do anymore is just lumber around and stop the run.

Interior pass rushers are becoming more and more important, especially as offenses are increasingly adapting to the more traditional outside edge rushers.

Take the Manning brothers: Among the many gifts the older brother has and the few gifts the younger has, the ability to scramble is a gift neither was given. Yet Peyton Manning leads all active QBs with a sack percentage of 3.1%, and Eli is not far behind, ranking fifth with 4.8% - and this has a lot less to do with their offensive lines than you may think. Instead, it has much more to do with the fact that while neither is a good scrambler, both are very good "shufflers", for lack of a better term. Sometimes all it takes is two small steps up or two small steps to the side to avoid the pass rush - as long as the pocket holds. Eli and Peyton both do this really well.

If all a QB has to do to avoid the pass rush is step up in the pocket, and you can't bring pressure up the middle, then you've got a pass rushing problem, and weight alone isn't going the help you with that.

The Cowboys will likely enter the season with a comparatively light defensive line. Hopefully, that will allow them to be quick off the snap and get pressure on the QB frequently, instead of getting pushed back or aside by bigger and heavier offensive linemen. But it wouldn't hurt if their edge rushers bulked up a little bit too.