The technical details in this article go far beyond my personal level of football expertise. Many thanks and a lot of credit goes to Steel34d, who not only answered my initial set of questions, but also the follow-ups and the follow-ups to the follow-ups.

I am also indebted to the authors of these four articles, which I can recommend to you wholeheartedly:

Actually, please do go and read those articles. I would really like to see the authors get extra clicks as a form of collective thank-you.

Defining some terms: "Gaps," "Techniques," "Two-Gapping and One-Gapping," and the stereotypical body types.

The blue capital letters refer to "Gaps". The A-Gaps are between the Center and the Offensive Guards, the B-Gaps are between the OG's and the Offensive Tackles, and the C-Gap between the OT and a Tight End (if there is one). The D-Gap is the space outside the TE.

The red numbers on the other side refer to the "Techniques", or starting positions, that may be used by defensive linemen. 1-tech defenders aim at the A-Gap; a 2-Tech defender lines up directly over the OG; a 3-tech aims at the B-Gap, etc.

As a general rule, D-lineman require more size and less mobility as their base position gets closer to the Center. The ultimate example is your stereotypical, 350 pound, immovable colossus of a 0-tech Nose Tackle. Another general rule is that certain techniques (0, 2, 5, and 6) tend have "two-gap" responsibilities. This means that a DL lined up as a 2-tech will probably be asked to control both the A- and B- gaps to either side of the OG he's facing. It's hard for a two-gapping lineman to actually make the tackle or get pressure on the QB. Instead their job is to make it easy for a linebacker to come charging in and either "fill" the opening on a running play or blitz through it on a pass. (N.B. I believe the odd numbered 5-tech becomes a two-gap position because the pocket is round. If you want to go directly through the OT toward the center of the pocket, you need to line up on the OT's outside shoulder).

Two-gap duties require a body that is long enough to hold the man in front of you at bay, strong enough resist the inevitable double-teams, and athletic enough react when the blocker tries to shift one way or the other on an angled block. This is why true Nose Tackles who can both play the 0-tech position and also chase down QB's are so highly valued. There are very few men on the planet who fit that description. Think Dontari Poe, Haloti Ngata, or a young Casey Hampton. They always get picked in Round 1 because they are three-down players in addition to "mere" run stuffers. An immovable colossus who can't chase people down will typically get picked in a later round depending on how far along he is. They are still vanishingly rare, but they can be schemed off the field by offensive formations that require more mobile defenders.

The classic 5-tech lineman is longer and a bit more athletic, like the 6'6" 305 pound models that the Steelers adore (who usually come with a basketball background as evidence of their movement skills). They can go at any point in the draft depending on how good they are at the 5-tech job, and how versatile they are at shifting to other spots on the line.

The stereotypical two-gap defensive lineman lives in a traditional 3-4 defense. "One-gap" defensive tackles are more common in a 4-3. Their primary job is to shoot through the A or B gap with so much speed and power that they gain an angle on the opposing lineman. 1-tech DT's tend to be a bit smaller and quicker than 0-tech NT's. They are usually assigned a slightly smaller premium, and the best are typically graded as late Round 1 to early Round 2 values. 3-tech guys like Aaron Donald can be downright short so long as they are stunningly quick. Their value is measured by explosiveness and strength above all else, and the best will rarely make it out of the Top 5 or 10.

IMPORTANT DIGRESSION: That's how the descriptions go in the mythical world of X's and O's. It doesn't work that way in reality because the patterns break down when you get to actual players - especially the ones who have the kind of peculiar athletic genius that gets them picked in Round 1 of an NFL Draft.

The young Casey Hampton could have played just as easily as a 1-tech or even a 3-tech because he had astonishing mobility for a man that big. Joe Green was the greatest 3-tech who ever lived. No one sane doubts that he could have played the 0-tech NT position too, or the 5-tech DE spot. Cam Heyward can also play anywhere along the line even if he's best as a 4- or 5-tech. It looks like the same is true for Stephon Tuitt.

Fans who like to play Junior GM (like Yours Truly) need to keep this in mind. Great talents cross and blurs the lines. Yes, there are limits. Aaron Donald and Geno Atkins can play any one-gap position on the defensive line, but neither has the sheer length required for a two-gap position. Thus the patterns are only vaguely true for any 1st Round talent. They grow more true, but still only as generalizations, as you move toward the later rounds where the players are a bit less versatile.

The Pittsburgh 3-4 and How It Has Changed

The Pittsburgh 3-4 defense of the 1990's and 2000's played the "Okie" system that came to epitomize the 3-4 approach. It begins with a space-eating, 0-tech NT like Casey Hampton who is supported by large, long and athletic 5-techs such as Aaron Smith and Brett Keisel. All three had two-gap duties designed to soak up blockers and allow the linebackers easy access to both tackles and sacks. This is Mr. Bowen's sketch of how it worked:

The modern Steeler 3-4 uses an "Eagle" front instead. Here is Bowen's sketch for that:

Note that the DE's are now lined up in a one-gap spot: the 4-tech directly over the tackle (actually the 4i to indicate a slight shading toward the inside). The linebackers are the one with two-gap duties. The strong-side linebacker has to two-gap the blocking Tight End, and the two ILB's have to move along the play ("scrape") and then choose which gap to hit. [N.B. This is one of the main reasons why Pittsburgh DE's have started to produce more sacks while it's OLB's have been accounting for less. The coaches have chosen to allocate the sack opportunities in that manner].

But of course it's not that simple.

Those patterns describe the "base" 3-4, meaning the one that the Steelers play most often. You know what it takes for the defense to convert back from Eagle to Okie? About half a step out by the ends and the strong side linebackers. In other words, next to nothing. And the Steelers shift like that with great frequency because it confuses the offensive play calling and blocking schemes. Pittsburgh will also use other variations, such as the 3-4 Under Front described in the 3-4 Article.

In other words, there is not "true" or "base" formation in the modern Steeler defense beyond the general description that it uses three down linemen. But that's not all.

Want to blow your mind? Start from the Eagle 3-4 and bring Bud Dupree down to be a 7-tech on one side of the line. Now drop Jarvis Jones back half a step on the other. Know what that is called? A classic 4-3 with 3-4 personnel, right down to the idea that the inside linemen should do their best to shoot through the A- and B-gaps instead of two-gapping in a 0- or 5-technique. Then there are "hybrid" fronts pioneered by Seattle, which are basically a hard-to-explain mix of 1-gapping and 2-gapping players mixed together in a 4-man front.

The reality is that we fans have fallen behind in our nomenclature. Defensive schemes have become so fluid that the names are pretty much all out of date. What Keith Butler does in the modern Steeler defense is a mix of concepts and tactics more than the installation of any particular "system."

But what about the "sub packages" we hear so much about?

"Sub packages" occur when a team removes either a defensive lineman or a linebacker in exchange for an extra defensive back. The variations are endless and depend to a huge extent on available personnel. For example, you get one package with an extra Safety on the field and a very different set of strengths and weaknesses if you substitute in an a third Corner. The new generation of Safety/LB hybrids fudge these definitions even more. Myles Jack is going to get picked in the Top 10 of this year's draft for precisely that reason. On running plays he counts as a linebacker, and on passing plays he's a Safety. Whoever gets him will be able to shift seamlessly from a 3-4-4 base into a 3-3-5 Nickel without any substitutions. For all the jokes about moving Ryan Shazier to Safety, the fact that he can learn to do the same thing was a major part of why Pittsburgh picked him at 1:15. (What could a team do with two of those hybrids? We might find out if Jaylon Smith's knee drops him to 1:25 in this year's draft or if Su'a Cravens falls to 2:27).

Then there are the differences between removing on of the defensive lineman (a 2-4-5 package) or one of the linebackers (a 3-3-5). Or... and... if... but...

The bottom line is that (a) juggling all these variations is why Coach Butler gets the big money, and (b) we Junior GM's need to realize that each man on the roster has his own unique set of skills and weaknesses. That is what the "Best Available Player" philosophy is really all about. Get the young men with the most extraordinary and/or most versatile talents, and then trust in your coaches to tweak the system in a way that will use their talents to the highest extent. Curse him all you like, but that is the core of what's made people call Belichek a defensive genius.

One thing that does play into this is a matter of philosophy. Which matters more to the front office: one exceptional skill, or a versatile toolbox that can be used in different ways? The Steelers tend to look for the latter. The F.O. has historically focused on multifaceted players who let the coaches use multiple defensive tactics with the same set of personnel. Other teams look more for specialists who can come in and do one particular job at an exceptional level. Seattle is a good example. Both approaches work.

The Steelers' 2-4-5 and 1-5-5 Sub Package Looks

Way back in 2009 a BTSC poster named Romain El 82 did a Fanpost on the "new" Steeler sub package looks. The 1-5-5 look is the infamous floating amoeba. I leave you to look at the Fanpost for more. The 2-4-5, however, has evolved into a fairly common package and therefore deserves a deeper look. I will let you in on the conclusion right now: finding someone to rotate in for sub package work is a major goal of the Pittsburgh draft, and it will be hard to find such a player after the first two rounds.

We saw above that the 3-4-4 personnel package has several optional formations built in. The same is true of the 2-4-5 Nickel. So this is another case where I'm talking about what is more common rather than what is true and false. With that said, the vanilla version of the Steeler Nickel presents two DL's in a two-gapping 2-tech position (aligned directly over the OG's). The idea is to have those two defenders hold up against all three interior offensive linemen (the Center and two OG's). Since it's a two gapping role you'd typically want long and strong players with the athletic ability to move from side to side if a play goes off-tackle. And since it's toward the inside you'd want players somewhat larger than your standard 5-tech. What you don't need is an explosive penetrator.

The Steelers almost inevitably relied on Cam Heyward and Stephon Tuitt to be that front-2. It added up to a lot of snaps over the course of the year. So much so that even Heyward was asking for help by the time the season ended. They did not get these snaps because they are DE's, they got them because they are both extraordinary athletes. The versatility to play both the 5-tech and the 2-tech at such a high level is very rare. When Tuitt got hurt, Steve McLendon stepped in as a natural 0- or 1-tech guy moving out to the 2-tech position (versus in from the 5-tech). He did the job adequately enough but there was a noticeable step down. It's one of those cases where a "very good" player is simply not the same as an "almost great" one, and the difference is easy to see. Cam Thomas had a few shots at this too. The difference was even more profound.

I'm not sure there is such a thing as a "pure" 2-tech player, and if there was the Steelers would hesitate to draft him. What they will be looking for are the measurements and athletic talents. A 5-tech with the ability to move in would be fine, and would also serve as a rotational backup for Heyward and Tuitt in the base 3-4 personnel package. A NT with enough movement athleticism to slide along the line would also do the job, a la McLendon but possibly that little bit better. But leaving this draft with no one who can rotate into the defensive front on Nickel downs would be a recipe for disaster. One season ending injury to either Heyward or Tuitt could easily reduce a Super Bowl favorite into a squad with a serious hole.

Could the Steelers Do Something Radical in the 2016 Draft, Like Picking A 3-Tech?

This part is based on Matt Bowen's 4-3 Article. I'm going to be even briefer than I was before because what I'm trying to get at is the question that follows.

A good 4-3 defense is built on two Defensive Tackles who line up in the A- and B-gaps, on the outside shoulder of the Center and Guard respectively. The 3-tech who penetrates into the B-gap is the one who gets the big money, though both matter a lot. The model 3-tech is a player like Geno Atkins or Aaron Donald; massive yes, but above all possessed of a first step so quick that the Center and Guards routinely need help from other linemen. It's another way of creating the same kind of numbers advantage we saw from the 2-gapping approach the Steelers had. FWIW, Joe Greene was probably the best 1- and 3-gap penetrator in the history of football. He often commanded triple teams.

3-tech penetrators do not fit a two-gap style of defense, just as two-gapping 0- and 5-techs do not fit your classic 4-3. That is what pundits mean when they say a given defensive lineman is great for one kind of defense but not for the other. And now it's time for that question: Why not try to use both tactics?

I said above that the definitions we grew up with are outdated, and that clever coordinators focus more on the mix of talents and tactics than they do on particular systems. Keith Butler is a lot more than just "clever." So none of us should have any doubt that Butler would find a score of wicked ways to Geno Atkins if the football gods dropped such a player into the Pittsburgh lineup. So why not try?

BTSC has an endless debate about this every year. What should Colbert do if a premium 3-tech talent happened to fall to Pittsburgh's pick? I can summarize it from memory. One side inevitably points to the salary cap realities. Treating a guy like Aaron Donald or Cam Heyward as a specialist means removing him from the field at all other times. The salary cap would eventually make it impossible to retain a talent like that at an acceptable price-per-snap salary. The same people then add that putting a specialist onto the field amounts to a giant "Caution!" sign that warns the offense what's coming.

The other side then points to teams like the Seahawks. The idea is, "You may have an easier time figuring out what we're going to do, but good luck stopping it." Which is better: a "special" 3-tech, or a "mere" 1st-Round talent who can do other things too?

Whether it's really a preference in the Front Office or the simple fact that prime 3-techs go off the board so quickly, the team has not been presented with a real dilemma about whether a penetrating DT would provide the most bang for its 1st-Round buck. This year might be different. Consider:

There is a short-term solution to the salary cap part of the problem. Rookie contracts. If the Steelers drafted a top-notch 3-tech, they'd have him for about 4-5 years before the salary cap realities made it impossible to maintain the unit intact. That's not a great way to build your team long-term, but at this point in Steeler history the team has a franchise QB with just about that much time left before he retires.

Another factor is the general need for depth on the defensive line. There is room for a special talent to carve himself a special niche without displacing a valuable generalist who is already on the roster.

Third, we know that Coach Butler is willing to make changes, like using a bit more of the Eagle 3-4 and a bit less of the Okie that Coach Lebeau pioneered. Might he also be willing to rotate in more specialty players in a Seahawky approach?

And then there's the fact that this year's defensive line class has an extraordinary amount of quality in the first three or four rounds. With so many linemen to choose from the odds are that much better that a "special" 3-tech will be available when the Steelers go on the clock. If there's a "special" 3-tech on the Board and a "mere 1st-Round" 0- or 5-tech, what would be the proper move? The prospect who offers more bang per snap, or the one who will give you more snaps and a longer Pittsburgh career?

Pittsburgh's "Wants" Going In To The 2016 Draft

If we assume that Steve McLendon gets re-signed, the Steelers will go into the draft with a number of "wants" but no particular "needs" along the defensive line. Here is a summary of what the roster will look like going into the draft:

Cam Heyward. A perennial all-pro DE in the making, and an ace in the 2-4-5 sub package.

A perennial all-pro DE in the making, and an ace in the 2-4-5 sub package. Stephon Tuitt. a bookend DE who's barely a year behind his linemate in the base 3-4-4 and almost as good already in the 2-4-5 sub package.

Then there is:

Steve McLendon. A solid (if improvable) NT with the ability to be a quality backup at DE and to play in the 2-4-5 sub packages.

The problems start after that, and they are not the sort of thing that the team can leave alone:

Dan McCullers. He could mature into a great, immovable 0-tech NT. Or not. We've seen ample evidence of both. But despite his extraordinary length we've seen no evidence that he has the mobility to double as either a 5-tech DE in the base package or as a 2-tech in the Nickel.

He could mature into a great, immovable 0-tech NT. Or not. We've seen ample evidence of both. But despite his extraordinary length we've seen no evidence that he has the mobility to double as either a 5-tech DE in the base package or as a 2-tech in the Nickel. LT Walton. Rumor has it that LT Walton is going to be a much better player than his late round position in last year's draft would suggest. He may well be a viable backup as a 5-tech in the base 3-4. Hopefully he will. Guessing that he will be more than that is heading toward the world of fantasy for now. He can't be projected as a backup NT, nor as a rotational 2-tech in the sub package game.

Rumor has it that LT Walton is going to be a much better player than his late round position in last year's draft would suggest. He may well be a viable backup as a 5-tech in the base 3-4. Hopefully he will. Guessing that he will be more than that is heading toward the world of fantasy for now. He can't be projected as a backup NT, nor as a rotational 2-tech in the sub package game. Cam Thomas . I'm not a hater.

I'm not a hater. Clifton Geathers . I'm really not. A realist, yes; a hater, no.

"Finding someone to rotate in for sub package work is a major goal of the Pittsburgh draft, and it will be hard to find such a player after the first two rounds."

In short, Pittsburgh has room for all of the following improvements:

WANT #1: A #3 DE who can rotate in with Heyward and Tuitt in the base 3-4. If we are lucky this could be LT Walton.

WANT #2: A better Nose Tackle than Steve McLendon, who is good but not great. Note that this would simultaneously free McLendon up to serve as the world's best across-the-line swing player (see Want #4). We aren't yet sure if Dan McCullers is a viable backup to McLendon. Projecting him as a substitute is a much bigger stretch.

WANT #3 - A talent good enough to rotate with Heyward and Tuitt in the 2-4-5 Nickel and other sub packages. This is the biggest hole, and the one that definitely is not on the roster right now. It's also a hole that won't be fixed outside of the 1st or 2nd Round. On the other hand, it could be fixed as easily by another great 5-tech DE who can move inside, as it could be by a great NT who can slide outside. In other words, an answer to Want #3 will almost certainly sole Want #1 or Want #2 at the same time.

WANT #4 - A flex player who could back up at any spot across the line. Heyward, Tuitt and McLendon all have the ability to do this but are too valuable as starters to be considered that way. Anyone who can fill Want #1 or Want #2 would thus free a current player to be the defensive multitool even if he didn't have that ability on his own. This is also true of LT Walton and Dan McCullers. If either of them can step up in 2016, the team's overall depth on the defensive line will improve dramatically.

WANT #5 - A penetrating 3-technique who would add new spice to the 2-4-5 package and allow Coach Butler to rotate into true 4-3 looks as desired. A true long shot, but what the heck. I'm a blogger, right? It's my job to create controversy.

The Soon To Be Legendary Defensive Line Class of 2016

And finally, the elite 3-tech guys who could make a real difference in sub packages but would not play in the base 3-4. All of the following players have the skill to be picked in Round 1 by a needy 4-3 team.