In the NFL, and football in general, defensive lineman play one of two techniques: one-gap technique or two-gap technique.
One-gap linemen are expected to penetrate off the ball and disrupt one hole along the offensive line. Ideally, a one-gap defender will split his gap and create havoc in the backfield.
Two-gap linemen have an ancillary role. Their job is hold the point of attack and control gaps on either side of their blocker. The play the role of space eater, adjusting to plays as they develop and allowing linebackers to be the playmakers. A quality two-gap defender will command double teams in the run game, leaving less offensive linemen to block the linebackers.
One-gap systems are typically deployed in 4-3 defenses, while two-gaps techniques are common to 3-4 schemes.
The Chicago Bears have never used a 3-4 defense in the 94-year history of the organization and that won't change this year. Yet it appears the team is in the midst of making a fundamental switch along the defensive line, from one-gap to two-gap.
"Schematically in the offseason we're putting in a system of football where we have to be able to stop the run first. That's where we're focused," coach Marc Trestman said during this year's NFL Scouting Combine. "That goes into the fundamentals and techniques and getting the right players as we evaluate them to get that done."
After being selected with the 51st overall pick this year, Ferguson discussed his first meeting with Chicago defensive line coach Paul Pasqualoni.
"[Pasqualoni] brought me to the office and we were basically just talking ball for the long time," Ferguson said. "He asked me, ‘Can I play that 2-technique? Can I do it? That's what they want me for'. They showed a lot of interest."
The term 2-technique is another way of describing a two-gap nose tackle.
Stephen Paea, who has been the team's starting nose the last three seasons, said he'll have a different role this year as well.
"I'm pretty much like a linebacker, playing smart on the defensive line," Paea said during OTAs this week. "We don't just play gap-to-gap, one-for-one. We're out here helping the linebackers and things like that."
There we have it. Bears nose tackles will no longer be asked to penetrate in the backfield. Going forward, their role will be similar to that of a 3-4 nose, to eat up double teams and give the linebackers room to roam.
"We hired Paul Pasqualoni and [LB coach] Reggie Herring. These guys have 3-4 backgrounds," Trestman said at the combine. "We think we've put together a staff of guys who can really incorporate and be flexible with the players we're going to have going through this process. We're going start from the 4-3 but we've got to be flexible in our scheme to move people around and have the ability to get it done."
Defensive coordinator Mel Tucker said during rookie minicamp he's installing "significant changes" to the defense this year. That obviously starts up front with the technique of his defensive tackles.
This strategy could compromise the pass rush, which is bad news for a unit that finished last in the league in sacks in 2013. The time Chicago's defensive tackles take to read and react to plays will be precious seconds they could be using to get to the quarterback. That's apparently a risk the Bears are willing to take, as run defense comes first under Tucker.
Two-gap techniques aren't common in 4-3 systems, so it's clear the Bears want to use hybrid schemes this year, which is why GM Phil Emery constantly preaches the value of finding players who "transcend schemes."
It's a fine line to walk and there's really no way for us to predict how this is all going to work out. One thing is for sure though, good or bad, the Bears will be very interesting to watch on defense this season.
Jeremy Stoltz is Publisher of BearReport.com and a member of the Pro Football Writers of America. He is in his fourth season covering the Chicago Bears full time. Follow Bear Report on Twitter and discuss this topic on our message boards. To become a subscriber to the Bear Report Web site or magazine, click here.