As you may know the Jets have not played a 4-3 scheme since the 2006-2007 season under legendary ESPN commentator Herm Edwards. Since then, they have played a passive 3-4 under Mangini, and then a fully aggressive 3-4 with Rex. If the Jets do decide to go to a 4-3 it's going to be a totally new feel for the linebackers and a lot of new responsibilities.
Let's start off with the 3-4. There are multiple ways a 3-4 is used, however, the base concept is that the 3 lineman eat up the blockers. They basically are needed to fight off double teams all while penetrating. It's almost their job to not only clog up a hole, but push two guys back and stuff a run/pass. It's also very rare to see a totally dominating 3-4 lineman with a ton of tackles. <ostly the lineman disrupts everything and leaves the tackles for the guys behind him.
The linebackers in the 3-4 must be quick, smart, and most of all: hungry. Hungry for the ball carrier that is. They make the difference on defense either by stuffing runs, making correct reads to the ball carrier, or dropping back into coverage. Because of the complexity of the 3-4, I'm going to break down the positions into ILB and OLB later individually. However, the main thing to remember is that 3-4 linebackers are tied to gaps and must make reads and hit gap assignments rather than blindly following the ball.
Now the opposite: the 4-3 requires excellent and disruptive line play and requires the linebackers to be mostly used in pass coverage rather than pass rush. Now the most important positions flip to the defensive line.
Instead of being just bodies in front that need to eat up blockers and penetrate, defensive linemen in the 4-3 must be physical forces who get into the backfield at will and can make life rough for the offensive line. While that may seem easy, remember that in a 3-4, you're not sure where the 4th guy is coming from. Now you know where the 4 guys are coming from and have 5 to block them.
Linebackers in the 4-3 are more free to roam then in a 3-4. They must be able to go sideline to sideline and be able to make tackles on the run. Unlike the 3-4, they are less worried about gaps and more about getting the guy upfield. Think Ray Lewis, who despite whatever opinion you have of him, was possibly the best at getting sideline to sideline and making tackles in the backfield. They also must take on blockers right away in the hole taking on blocks in the running game. Unlike the 3-4, linebackers, the 4-3 requires the inside linebacker and outside linebacker to fight off either a lineman or FB to make a block.
The alignments are also very different (this is mostly to show base concepts, obviously there are wrinkles)
In the 3-4 the nose tackle is typically head up with the center, while the two defensive ends are typically over the offensive tackles. Two outside linebackers play off the tackles to the outside but near the line of scrimmage, while the two insider linebackers play inside near head up with the guard 5 yards back. Here's a visual:
In the 4-3, things do change a bit. Mostly there is an offset, unlike the 3-4 which can be played almost straight up. Notice the NT is now offset, the defensive tackle plays mostly off the guards shoulder in the C gap, and the two defensive ends are more to the outside than the defensive ends in a 3-4. The inside linebacker (middle linebacker) shifts and plays over the center shoulder, while the two outside linebackers play over the tackles shoulders. It makes a lot of difference in how they play from where they align.
Now we have the basics done: meaning that now we can really get into the fun part.
Time to break it down position by position starting with the 3-4.
Nose tackle: The fat cat. This guy must be big, strong, and in beast mode. This guy faces the most double and sometimes triple teams and must fight him off. Think Vince Wilfork or Pouha in his prime, big strong guys who can beat a double team sometimes while not getting pushed off the ball at all. The Jets used a rotation at most of the line positions, although Kenrick Ellis seems to be the most prototypical 3-4 nose tackle now that Pouha and Devito are off the roster. Garay also fits in real well into this role, but I think is going to be used as the backup.
Defensive end: Here is the position the Jets are stacked at. Defensive end must do the same things as the nose tackle except must also be good at pass rushing and at getting into the backfield. They must also be big and strong, however they must also be able to fight off double teams to get the job done. However, unlike the NT whose job is basically to clog the middle and provide some rush, these guys must provide it. They tend to be smaller and quicker than true NT's, so they can disrupt plays in the backfield. This is probably the second most important position in the 3-4, because they must be strong enough to not get pushed back, but provide a ton of rush by themselves.
Outside linebacker: The outside linebackers must be spot on with the reads and get into the backfield to be successful.They are truly the defenders that make or break the defense. A good 3-4 defense needs two outside linebackers that cover the gaps created and stuff the run on running plays. Part of what makes a good outside linebacker is the ability to set edges on the run, something Rex always praised about Bryan Thomas.They have outside gap responsibility in runs, which forces them to set the edge and turn the run inside to the bigger guys. Circa 2009-2010 Jets is a classic example of a good run stuffing outside linebacking corps. Why is this so key? If a guy gets outside, it's game over.
Example: watch the OLB get sucked inside. No one is there outside and Greene walks into the endzone because the OLB committed inside and it lead to a quick 7.
The problem is that is only half the battle. They also must be excellent pass rushers, something Calvin Pace was brought in for, and never lived up to. They must be able to get by the tackles, not just by firing by the outside, but by also beating the tackle one on one. As a general rule of thumb: Outside linebackers are much more needed then inside linebackers at pass rushing in the 3-4. This is the one area the Jets have never quite found a guy. John Abraham was the last true guy, but he played defensive end in the 4-3. Since then, nada.
However, I did find one example of how an OLB should impact the QB. Check out around 1:20 mark and Calvin Pace track down Brady. He laid him out, after a great rush.
Inside linebacker: Inside linebackers in the 3-4 must be great gap shooters. They must be able to read where the ball is going and fire into the gap stopping the play. Because the lineman eat up the line, it's up the inside linebackers to fill the inside holes and stuff the run. However, they cannot simply rush a hole, they must be excellent readers of the play. David Harris, who despite losing a step, is still tops among read and reactors. He can fill holes quickly, but doesn't over commit. In this defense the inside linebacker is strictly tasked with the inside gaps in the running game and can focus on those.
In the passing game it gets interesting for the inside linebackers. Generally speaking, in Rex's defense the inside linebacker is mostly covering a back or tight end but occasionally blitzes in a scheme. Harris. despite being a great run protector is not that great in pass defense, and now with a question mark at the other inside linebacker position, it begs the question of how can we defend against good tight end and running back play.
Time to break down the 4-3 position by position. It must be said again, in the 4-3 the defensive line is charged more with than just eating blockers. Now they are the ones who must create pressure.
Nose tackle: He must be big, but arguably must also be quick. For comparison's sake, it's mostly a hybrid between the 3-4 nose tackle and defensive end leaning more to the nose tackle. Unlike the 3-4, this guy must be able to penetrate. His job simply isn't just to eat up two blockers, he must be able to also get in the backfield in running and passing downs. Kenrick Ellis in this defense may go to waste, he doesn't seem to offer as much as a rush as needed. However, our newest Jet should be a great fit for this nose tackle position.
Defensive tackle : The defensive tackle is more like the defensive end in the 3-4 than a nose tackle, but still must be big enough to fight off the offensive guard and offensive tackle. However, again it's more than just eating blockers, he must be able to rush. The run responsibilities aren't just limited to stopping guys from getting to the second level, it's also about getting into the backfield and forcing the running back backwards. Wilkerson is probably the best example we have of a true 4-3 defensive tackle. He can rush, eat blockers, and be a force. Ideally you can easily slide him into this role.
Defensive end: These guys are a combination of outside linebackers and defensive ends in the 3-4. I'd say 75% outside linebacker and 25% defensive end in a 3-4. They have to be big enough to be the primary run stoppers, but also be great pass rushers. The nose tackle and defensive tackle will eat up most of the blockers which would allow the defensive end to have one on one matchups with the offensive tackle. This is where the defensive end must shine. A good defensive end can cause problems. A great one requires the offense to shift help. The defensive end is by far the most important position in the passing game. However, that's not to say the defensive emd must not be good at the run, now the outside contain requires the defensive end to force the play back inside, but not get caught on the outside and give up a big hole. Arguably, the Jets may have Coples who can play this role, and you're not going to like this: but the only other guy I see being able to slot in the role is Calvin Pace. I'll get to this below.
Middile linebacker: This is where the bread and butter position of the 4-3 defense is. If defensive end is 1A for a 4-3 to succeed, than the middle linebacker is 1-AA. This guy must be fast, a great reader and better yet, and great athlete with size. Ray Lewis and Urlacher are the best examples.
This guy must be able to cover just about the whole area in between the hashes in the running game. That's the main difference. In the 3-4 the inside linebackers have to cover only the middle gaps in the offensive line. The middle linebacker must cover the middle part of the field and be able to go sideline to sideline. Why you might ask? Because once you get past the first 4 lineman now there are only 3 guys before you get to the secondary. Now instead of covering the run with 4 linebackers now you have 3, meaning more field to cover per person.
Here is what I mean in a 4-3:
In the 3-4 mostly inside responsibilites:
In the 4-3 though the middle linebacker is mostly left to defend the pass by not rushing but by staying in zone or man. Because this defense relies so heavily on the defensive line for a rush it's not always necessary to bring more than 4 unlike the 3-4 defense.
Outside linebacker: Unlike the 3-4 these guys aren't as critical. They still must be able to provide good run support but need to be bigger than the 3-4 outside linebackers whose primary goal is to provide pressure. These guys are mostly like the inside linebacker in the 3-4 but faster. They must be able to get to the sidelines in run support and also provide good pass defense similarly to that of the middle linebacker in the 4-3.
Let's recap the position by position differences between that of the 3-4 and 4-3.
Nose tackle: 3-4 must be bigger able to take on double teams. 4-3 must be a tad more agressive into the backfield.
4-3 defensive tackle/ 3-4 defensive end: The 4-3 defensive tackle is simliar to that of a 3-4 defensive end but more aggressive and a touch bigger. The 4-3 defensive tackle must also be more inclined to get into the backfield and disrupt the play
4-3 defensive end and 3-4 outside linebacker: Similar in style but very different in practice. Both must be able to rush the QB. 4-3 DE must be bigger but 3-4 DE must have better pure speed and quickness
3-4 inside linebacker and 4-3 middle linebacker: No comparison. Totally different responsibilities. 3-4 ILB are bigger, quicker and focused on the inside holes. 4-3 MLB are faster and must be able to move laterally.
4-3 outside linebacker: Similar to that of of 3-4 inside linebacker but much faster and can be smaller. 3-4 outside linebackers tend to be smaller than the 4-3 due to the pass rush needs.
That being said how do the Jets fit in a 4-3 with the personnel they have now?
I'd argue it's roughly the same either way: we're hurting/doomed. I think that by switching to a 4-3 would require a bunch of players to be out of position and probably really cause some catastrophes.
The Jets have David Harris, who hasn't played a 4-3 probably since HS at the earliest and was a beast up until a few years ago in the 3-4. The 4-3 needs linebackers to cover the passes more and Harris has never been a great cover guy. The outside linebackers in a 4-3 need to be good in coverage, so that seems out too. The worst part is Harris to me doesn't have the speed to be good enough to play the 4-3 middle linebacker or outside linebacker. He'd be a fish out of water in the defense. And the best position for him might be on the bench, which with his contract...ouch.
Looking at the current crop of linebackers outside of Harris, I really don't really see much in terms of great coverage guys on the roster. Mauga is probably too slow to be good in a 4-3 middle linebacker role, but can probably be slotted over into the outside linebacker in a pinch. Davis is the interesting one, as he could probably be put in the middle instead of Harris.That could work with Harris moving to the strong side outside linebacker, if you wanted Davis to be the key to the linebacking corps. Again though, I can't see Harris being great in any linebacker role in the 4-3. Barnes our FA pickup is probably too small for the outside linebacker plus he's more of a pass rusher than run stopping threat. I'd argue we're not helping ourselves in the linebacker department, even though Davis may be able to play middle linebacker in the 4-3.
The 4-3 line is fine on the inside: Wilk can easily be a great defensive tackle in the 4-3. I think he has the size, speed, and pure ability to be a great defensive tackle or nose tackle but would be much better suited for the defensive tackle role. Our new guy Sheldon Richardson is probably going to get the nose tackle role considering how good Wilk fits as a 3 technique, but could also rotate there. IMO Ellis would be left out as he is more suited for the 3-4 nose tacklethan a 4-3 role, but he would be the nose tackle backup role with Garay. Coples would easily fit a defensive tackle role but probably would have to be moved to the outside. Basically we'd be left with something like this rotation: NT: Richardson/Garay/Wilk DT:Wilk/Richardson/Coples.
On the outside things get interesting: Coples probably would be moved over seeing the logjam at 3 technique. Although Coples is arguably better on the inside, Wilkerson should not be moved from the 3 technique where he'd dominate. Seeing we need a 4-3 defensive end, Coples would be moved there, but is probably not going to be a world beater. I think he's much more suited for that of a 3-4 role, where he can beat a guy with speed, I just can't see that with today's crop of OT. He's much more suited for the defensive end in the 3-4 or defensive tackle in the 4-3.
Then the other side is a huge question mark assuming Coples goes to DE: Who can you play there? Pace is probably the best option which is problematic.(Trying to be diplomatic here). Barnes to me is just to small and would probably be without a true position in the 4-3, but could be slotted in a pinch. IE the Jets just don't have the right personnel to get a 4-3 defense without moving more than half the players from true positions.
The 3-4 presents other issues. Mainly can Mauga/ Davis step into the role of Bart Scott? I'm not 100 percent certain. You have an obvious lack of any starting material at one OLB and are counting on a part time player to step into a full time role on the other side. For my money though the 3-4 offers better options from the LB standpoint.
The defensive linemen for the 3-4 is stacked. With Ellis/Garay/Sheldon at NT and defensive endbeing a mix of WIlk/Sheldon/Coples this could be really a great DL. The possibilities are endless in rotations and matchups against offenses. It's scary how this line can go from run stuffers to pure pass rushers. Problem is the linebackers, which are key to the 3-4 are suspect, despite the line's possibility of greatness.
To wrap it up: The 4-3 would cause more headaches. We have 3-4 personnel. I know you can't fit four guys in the line on a 3-4, but it would seem to me that the 3-4 would provide a better chance for success.
Side note: for anyone who thinks the 46 is the wave of the future: Read my article on the 46 bear. Yes, this is a SHAMELESS PLUG for a previous article.