Evolution of the defensive end

In the modern era of the NFL, no more than seven defensive ends have been selected in the first round in a single year. However, ESPN NFL draft insider Todd McShay projects 11 defensive ends to go in the first round next week, which begs the question: Why the sharp increase? Could it be a cyclical result of the teams' current defensive ends aging, or an unusually deep pool of standout performers in the college ranks? It's possible, but the likely answer is something even more radical.

The nature of the defensive end is changing.

The job description

Defensive ends were once graded on their ability to stop the run and occasionally assist in pass coverage, but they now are asked to do one thing above all else: rush the passer.

Pressuring the quarterback has always been a function of the defensive end position; 77 percent of the players to record double-digit sacks over the past decade were defensive ends. The difference now is that coaches and front-office personnel realize the importance of that skill and are giving DEs free rein to do what they do best.

With so much recent emphasis on getting to the quarterback, other areas of the position have gone by the wayside. Passes defended by ends in the 4-3 scheme are in decline; they averaged about 28 fewer passes defended from 2008 to 2010 than they did in the three-year span before that. Tackles in general are also decreasing; defensive ends accounted for only 20.4 percent of all tackles last season, their lowest mark over the past 10 years.

The specialized, important role of rushing the passer has gradually resulted in a noticeable trend in the body mass of defensive ends.

They're getting slimmer.

From 2001 to 2005, there were more defensive ends who weighed 271 pounds or more than there were who weighed 270 pounds or less. In 2006, the ratio of lighter to heavier defensive ends became almost equal, and the trend continued until those weighing more than 270 pounds have become a rarity.

This wasn't an arbitrary decision (or possibly even a conscious one); it was the result of the position's emerging requirements. Perhaps a coach somewhere looked at the number of defensive ends who recorded double-digit sacks over the past decade and noticed most of them weighed less than 270 pounds, despite the fact the majority of the ends weighed more.

Even more telling was the weight difference seemed to correspond perfectly with the number of sacks the player was posting. Defensive ends weighing less than 270 pounds, on average, recorded more sacks than their heavier colleagues in each of the past 10 seasons.

The trend that's emerging is that the all-out sprint after the quarterback on every down necessitates a slimmer build than in years past. ESPN NFL analyst Herm Edwards explains, "you don't have to be a big guy anymore. If [defensive ends] can't play the run, teams can live with that. Just go and hit the quarterback."

Although height has remained the same (defensive ends have averaged roughly 6-foot-4 in nine of the past 10 NFL drafts), the pounds have fallen off in a consistent fashion. Last year's draft class of defensive ends averaged a full 13 pounds lighter than that of 2001, and the gradual change has taken the form of a linear slope.

Logic would suggest there's an obvious explanation for the weight loss, whether it's a result of health-conscious training staffs or more intensive workouts. Maybe all NFL athletes are slimming down. Striking evidence that points to the contrary can be seen when examining comparable positions to the defensive end: tackles and linebackers. Over the past 10 years, drafted tackles have remained constant around 304 pounds and outside linebackers haven't strayed too far from their 10-year average of 242 pounds. In fact, linebackers actually gained 6 pounds from the 2008 draft to the 2009 draft.

Re-emergence of the 3-4

More and more teams are switching from 4-3 fronts to 3-4 alignments since the versatility of the outside linebacker allows defenses to disguise pressure effectively. In 2007, about 30 percent of the NFL employed a 3-4 scheme; that number swelled to almost 50 percent last season.

Because a 250-pound outside linebacker is much more capable of covering a tight end or fitting into a zone-blitz scheme than a 280-pound defensive end (while still providing equal pass-rushing abilities), coaches are on high alert for these unique talents. There's a strong market for "tweeners," players who are caught in the crossroads between the outside linebacker and defensive end roles.

Drafting these undersized collegiate defensive ends and converting them to bulky, yet speedy, outside linebackers has become common practice. Tamba Hali and LaMarr Woodley are prime examples of this; their potent combinations of strength and speed give their defensive coordinators endless possibilities. McShay projects a few such picks in this year's first round, notably UNC's Robert Quinn and Arizona's Brooks Reed.

Beauty of the four-man rush

"Anytime you play defense and put pressure on the quarterback with four guys, you prefer to do that so you can drop seven guys into coverage. When you have the ability to rush four guys and one is able to get to the quarterback, that's a win for the defense," Edwards said.

Most four-man pass rushes in a base 4-3 alignment are executed by the down linemen, giving linebackers and blitzing defensive backs less of an opportunity to reach the quarterback. So one question I've asked myself while researching this topic is: If you're routinely sending the front four, shouldn't defensive tackles have just as good of a chance to record a sack as defensive ends?

Why then, of the 20 players to post double-digit sacks last season, were 19 of them either ends or outside linebackers? Only AP Defensive Rookie of the Year and future perennial-exception-to-the-rule Ndamukong Suh made the list from an interior line position. The answer lies in body mass. Ends can use agility and lateral quickness to beat their blocks, whereas tackles have to power their way through the offensive line. Try pushing a refrigerator on its side 75 times in three hours, or simply running around it.

The future of the position

In modern architecture, form follows function. It's a principle that suggests the shape of an object is dictated by its purpose. The trend we're seeing unfold with defensive linemen is this concept come to life. They've evolved into their current optimal condition as a direct result of their purpose.

The weight difference between defensive ends and outside linebackers has decreased by an average of 1 pound and 13 ounces per year over the past six years. They'll eventually strike a balance, but hypothetically, if they remained on that aggressive pace the positions would be indiscernible in 2026.

Whether teams have their sights set on a lean defensive end or a bulky linebacking hybrid, drafting a dominant pass-rusher seems to be a safe move, because they'll always be an integral part of the game.

After all, in today's quarterback-driven league, the defense's greatest weapon has to be the guy who can stop him.