There is much bally-hoo in the NFL circles about defensive schemes, and what type of prototypical athelete is required, its bunk, well most of it anyway. There are distinct differences in the schemes yes, but you might be surprised in the similarities of athelete required to play in those schemes successfully. There are differences however, one can certainly see that NT in 3-4 schemes tend to be bigger slower guys, shut down corners are almost a thing of the past for both formations as they are just too far and few between these days. Linebackers can vary greatly from team to team and most agree specialists are the key to success, lets look at each positions size and responsibilities and determine for ourselves what differentiates the 4-3 from the 3-4. Along the way lets look at what some of the assignments are like for these atheletes. Because understanding why your team selected who they did is just as important as knowing why they fail or succeed in the season.
The line, although the 3-4 and 4-3 are vastly different in their assignment and run lane schemes they do require somewhat similar skill sets from these atheletes. The true understanding of the differences lie in the second level of defense, or the linebackers which will be more fully covered in that section.
Players at this position can range from 270-290 in weight, todays end tends to be quick with good lower body strength for leverage. Speed over size equals success in todays NFL. These guys primary responsibility is to get after the QB. Most cover two and 3-4 schemes eliminate the need for these guys to contain the run, although the ability to do so is a plus.
300+ pounds able to penetrate with leverage and strength, typically used to occupy blockers so that LB'ers, can stuff the run lanes or take on short pass routes. Coined as one of the toughest NFL positions to fill simply because a player comes into the league with the size but he must adapt to not only the speed of the NFL game, but soon learns size is not enough, hand technique and foot speed, reading and adapting have to be developed, thus creating the great unkown factor, and when franchises are paying multi- million dollar contracts for draft picks, unknowns are not something an owner readily embraces.
Although similar in many ways to RE, the LE has two distinct assignments that rarely fall on the RE. One is jamming up the TE in passing situations and to contain the run pushing it back to the inside when possible. Because of these two additional duties LE should have good upper and lower body strength for maintaining containment on the runner, additionally good hand technique is a must to disengage from the blocker in order to wrap up the ball carrier. Size wise 270-290 in weight is still ideal, these guys tend to be taller/ have longer wing spans than RE but versatility of speed and strength makes a successful player here.
The rubber meets the road here in understanding the difference in the athelete and the schemes. The 3-4 typically needs a deeper depth chart here as LB is key to the success of the formation, the 4-3 specifically the cover two uses more specialized guys that are quicker. so 3-4 more well rounded atheletes, the 4-3 more talent specific, lets break it down position by position.
Size 250-290 pounds, with the lower end belonging to the 4-3 clubs and the higher end belonging to the 3-4 squads. In the cover two, being used by more and more clubs this position is the "playmaker" he has no run lane responsibilities he has one assignment, "find the ball". Now that is not to say he doesnt guard against the run or play his zone in passing situations, but his primary job is to be the disruptor. You will see cover two LOLB's racking up unreal stats as a matter of course, they will always be around the ball so tackles, ff, and INT's will soar. The trend, converted college safties make great LOLB's for cover two (smaller, quicker, good hands). Derrick Brooks, Cato June, Thomas Davis just to name a few. In the 3-4 however expect this to be a taller stronger guy, he sometimes has to line up at RE, and take on linemen, he has to be able to rush the QB, he has to be able to cover a pass route. Even in the 3-4 circles you are seeing teams going to specialists, rotating LB's based on down and distance, running plays will have LB (A) short passing LB (B) and pressuring the QB LB (C). These are the type situations you see the Carson Palmers and Peyton Mannings of the world trying to do quick snaps on while the defense is trying to make personel changes.
Prototype athelete will be 250-290 pounds, again the low range is a 4-3 LB the higher end is a 3-4 LB. These guys can be similar in size but their roles are different. In a 4-3 on a running play, the MLB is to stuff a specific run gap. On passing situations he drops 15 yards deep and plays center field disrupting any pass route within the hash marks. In a 3-4 formation, obviously there are two MLB's their assignments can vary from defending a rush lane, to blitzing to covering a TE one on one, so bigger hitters that are quick not necessarily fast, and they dont necessarily need good hands. The 4-3 guy needs speed and good hands everything else is just a plus. Additionally in some cover two instances the MLB can actually play the role of a 3rd safety, dropping into a deep middle zone.
Again 250-290 pounds, see a theme here, for the 4-3 LB, you are lining up on the point of attack you will have the TE in coverage, you will be expected to shed the blocker and take the runner when its a running play. For the the 3-4 you are the LE/ LB you may take the TE, you may blitz you may stuff a run lane, you may get a slot reciever on a stacked formation. It is a recurring theme that applies to the differences between the 4-3 cover two and the 3-4 defenses, the cover two is very vanilla, you arent often going to see surprises they average in the lower third of the league on blitzes, yet they they produce 50% of the sacks, its line up and beat your man football. The 3-4 however is deadly because you dont know what it is or where its coming from, anyone can blitz at any time, you will see lots of movement pre-snap for that very reason on a 3-4 they dont want you to know who is doing what.
The Secondary, This position may be the most universal in terms of how it is played, quote simply you are either playing man on man, or zone defense. The cover two is predicated on almost exclusive zone coverage, while the 3-4 uses man on man more often than not, but that isnt to say that they don't each reverse roles from time to time.
160-180 LB's, zone coverage or man on man that is the difference. Zone coverages typically are outside the hash marks from 5-15 yards off the line of scrimmage, but that is the typical there are some outside the norm formations that can distort that zone horizontally or vertically or both. The thing to know is, a cover two WILL NOT, Does NOT need a shutdown corner, its a waste of money and talent, the guy will be playing zone 85% of the time or more, who cares if can run a route stride for stride with the top 3 recievers in the league. the rub talent wise is, 3-4 guys will be more shutdown corner LIKE, cover two corners will be sure tacklers with good hands.
Size 200-230 LBs. Here is where the difference lies in the secondary between the two schemes. For the 3-4, the saftey positions act as a last line of defense, they will help double deep routes and make TD saving tackles on break away running plays and that is pretty much the extent of their responsibilities. Sure tacklers with good speed. The 4-3 however employs their safeties in other ways, it is not unusual to seem them bring the Safety up to the line if a run is suspected, or you may even see them blitz on occasion. Fast, hard hitters with sure hands are what is required from the 4-3. Think Troy Polamalu or Bob Sanders here.