Not all 3-4's are created equal
When people talk about a 3-4 defense, they are at the very basic level defining a defensive front. Three down linemen, four linebackers. You have two defensive ends, a nose tackle, two outside linebackers, and two inside linebackers. If I remember correctly the "original" 3-4 was invented and utilized in college football decades ago (originated with OU).
This "original" 3-4 defense had a very specific role for it's down linemen. Each end was a 4 or 5 tech that was a two-gap player to go along with a two-gap nose tackle.
What is "two-gap?" Two-gap for lack of a better explanation is "read and react." The player is responsible for the gaps to each side of his man and must read the flow of the play in deciding which to defend. He must be strong enough to hold his ground and not get pushed or sucked into the play, and he must be athletic and quick enough to get to the quarterback.
The first thing to understand about Wade Phillips 3-4 is that it is a one-gap system. The play call is made and the down-linemen attack. It is not read and react, players do not need to occupy space, read the play, then decide what to do. From the snap they are ready to attack.
In an interview with NFL.com, Wade described his defense:
"When I started out it was a two-gap defense, the defensive ends had to play two-gap and be able to rush the passer. Well that's a hard thing to do."
"We had a guy here with the Houston Oilers named Elvin Bethea," Phillips continued. "We said, ‘Wait a minute. We don't want to do that with that guy.' We started stunting the guys and moving them and let them do what they do well, playing a 3-4, but playing a different way, Phillips 3-4 if you want to call it that. I had another guy named Bruce Smith that wasn't bad at in a 3-4 You can do it with guys, if they have the abilities, then you let them go more. If they don't then you play a two-gap and just hold your ground all you can and let the linebackers make the plays. It's all about what kind of players you have and let them do what they do best."
What jumps out is the fact that while Wade runs a "system" the system is not what determines how Phillips uses his players, it's the player's skillset. This is one very understated characteristic of a good coach or teacher in my estimation--one who will get the best out of their player's by utilizing their skillset.
Look no further than J.J. Watt. Watt is 6'6" about 300 lbs and though he is listed primarily as a DE, he moves around the line to exploit mismatches. Watt is not your prototypical 320lb defensive end. In fact if he were to line up in a standard 4-3 he could be your undertackle.
What this means for the Broncos defense
Call it 4-3 under, 5-2, 3-4, the "look" of the defense on base downs will not change drastically, nor will the role of the players. The Broncos scheme under Jack Del Rio was similar enough to a hybrid front that we already have the personnel to carry out Wade's scheme. What will be a key going forward is to resign Terrance Knighton to play the NT role in the middle. From there, we could use players already on the roster to fill roles that they themselves have already become accustomed to. Both Derek Wolfe and Malik Jackson would make fine DE's in Wade Phillip's 3-4 base defense.
When looking at linebackers, I believe what he have is the potential for Wade to make another adjustment. On the outside, your WILB will be interchangeable with both DeMarcus Ware having already played the same role in Dallas under Phillips and Von Miller being able to rush from either side. You will not see these players drop into coverage as much as they did under Jack Del Rio.
Traditionally, a 3-4 employs some larger ILB's in the middle, but what about the idea of pairing Danny Trevathan (WILB) and Brandon Marshall (SILB) in the middle? Both players have already proven an ability to shed blocks and make plays at the line of scrimmage in the running game, both players give Wade something that has not exactly had before. Two cover linebackers that are stout against the run, who can also be utilized in blitz packages.
One of the primary concerns with the Wade Phillips 3-4 has been the ability of elite QB's to exploit the middle of the field with quick passes. Having a couple of coverage linebackers in the middle would go a long way towards neutralizing that threat.
Regardless, it opens the door up for players like Shaq Barrett who would excel as an aggressive ILB in Wade's scheme.
If the Broncos interest in Phillips goes as far as making him our next DC, I will continue to break down the Phillips 3-4. Until then know that it would not require a wholesale turnover of the roster in order for the Broncos to make the transition. In fact, here is your starting lineup:
CB 1: Chris Harris Jr.
CB 2: Aqib Talib
When going to nickel and dime, the Broncos will revert to a "four man" front similar to what you saw them utilize all season in their nickel and dime sub-packages.