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Al Groh is considered to be a leading expert on the 3-4 defense.
Just ask Bob Diaco.
The first-year Nebraska defensive coordinator worked under Groh as a linebackers coach at Virginia from 2006 through 2008. During his introductory news conference at NU in January, Diaco referenced Groh, describing him as a "great teacher."
Groh was Virginia's head coach from 2001-09. Before that period, he worked for four NFL teams from 1989 to 2000 — the Giants, Browns, Patriots and Jets — and coached some of the league's best defensive players, including Lawrence Taylor, Andre Tippett, Carl Banks and Willie McGinest.
Groh speaks highly of Diaco.
"Lots of energy," Groh said. "Lots of passion for football. Very organized."
Groh isn't familiar with how Diaco's 3-4 defense has evolved in recent years. But Groh can take you through the key elements of a 3-4, especially the Bill Belichick/Bill Parcells model that he learned — which is essentially the system currently used by Alabama.
"Which is basically a two-gap system with downhill inside linebackers and big, versatile outside linebackers," Groh said.
Retired from coaching and living right outside Boston, the 73-year-old Groh was gracious enough to answer some of our basic questions.
Question: You like to say outside linebackers in a 3-4 are like the 3-4-5 hitters in a baseball lineup. What do you mean by that?
Groh: In baseball, those are the major run-producers. In the 3-4, the outside linebackers are the guys who are supposed to get the RBIs — in other words, make the big plays in the offensive backfield, in the run game and in coverage. It requires a lot of attributes to fulfill all the aspects of the job description. It takes size. It takes athletic ability. It takes instincts. It takes a very versatile game to be a true outside linebacker. The guy can't be a one-trick pony. Certainly an integral part of the position is to be a dynamic pass rusher. But if all he is is a dynamic pass rusher, then what he really is is a defensive end.
A true outside linebacker has to be able to dominate the tight end area against the run, rush the passer and continuously disrupt the pocket, but also be an effective pass defender. If that outstanding pass rusher can't also be an outstanding pass defender, then the 3-4 defense loses its versatility of being able to rush any one of four linebackers to create your basic four-man rush.
Q: Why is the 3-4 typically considered a good pass-rush system?
Groh: With any defense — 3-4, 4-3, nickel, whatever it might be — your basic core pass rush is a four-man rush. So, in a 3-4, which one of those four linebackers is going to join the down three (linemen) to create the fourth rusher? There's a deceptive aspect in that, which has a lot to do with the success of, for instance ... You might be familiar with the Pittsburgh Steelers' fire-zone concept under (former defensive coordinator) Dick LeBeau. So much of that was based on putting together a variety of rush schemes in which the offense had to figure out, after the snap of the ball, which one of the four linebackers were going to come in on the pass rush. Or sometimes two of those four linebackers will join the three linemen to create a five-man rush. When you take away that versatility (of an outside linebacker) — because the guy is a one-trick pony — then you're not really a true 3-4. You line up like a 3-4 team, but you don't really play like a 3-4 team.
Q: Would you characterize the outside linebackers as the most important pieces of a 3-4 defense?
Groh: I wouldn't say "most important" because it takes all the parts working together to really create the effective 3-4. For example, it's not a glamour position like we talk about with the outside linebackers being your cleanup hitters, but it's hard to be a really good 3-4 defense without a really good nose tackle. That guy must have good lateral quickness as well as leverage, power and explosion.
Q: Why is lateral quickness important for a nose tackle?
Groh: Because that center rarely, if ever, during the course of a game or season is going to come off the ball straight ahead. He's always coming off at essentially a 45-degree angle to the side of the play. If the nose tackle has what most people associate as prototypical nose-tackle size, but he can't move laterally, then he's immediately cut off.
Q: What is prototypical nose-tackle size?
Groh: Six-foot-2 to 6-foot-4, 295 pounds or thereabouts. The player has to be able to play with leverage. Thing is, there are a lot of big guys who don't have leverage, explosion and power. Those attributes have to be there for actually any of the three down linemen. There are defensive ends who also have the attributes to play nose tackle. But there usually aren't nose tackles who have the attributes to play defensive end.
Q: The role of the inside linebackers seems cut-and-dried. They have to be good "downhill" players — strong against the run. Is that an accurate characterization?
Groh: I would certainly say that's important. But the first thing that inside linebackers have to be able to do to play in the defense is they have to effectively get the defense called, lined up and adjusted. All the other players in the front — the down linemen and outside linebackers — they're all waiting for the calls from the inside linebackers to specifically know what their assignment is. To play inside linebacker, a player must be really interested in learning all aspects of the defense.
Q: Are the jobs of the defensive backs in a 3-4 system much different than in a 4-3?
Groh: No. Coverage is coverage, regardless of what front scheme you choose ... There is no typical 3-4 coverage. It all depends on the philosophy and style of what that coach wants to play in the secondary.
Q: One last thing: Is there anything in particular that distinguishes Alabama's 3-4?
Groh: (Chuckling) Yeah, the players.