Here is an interesting concept from legendary Titans' Defensive Coordinator Dick LeBeau. The Titan's are a base 3-4 structure. However, they very rarely look like the 3-4 diagrammed below.
The Titan's use their base personnel against run heavy personnel groupings.
Often against these formations the 3-4 reduces the front, playing the OLB's at the LOS to create the under front and other base defensive structures.
Against spread formations with 10 or 11 personnel the Titans will sub to a Nickel or Dime package.
While it may look like the normal 4-2-5 defense there are some differences. In the NFL most of the 3-4 teams sub out the Nose for the 5th DB. The DT's in this diagram are the ends in the base personnel grouping while the Ends in this package are stand up OLB's. Subbing into a 4 man line nickel package does have a some limitations. One being the defense can't bring 3 down odd front pressures from an even front.
The Titans have a solution.
Tennessee is using the sub nickel package but bumping the front to create an odd front look. This concept allows the defense to bring pressures like:
Mike & Will - Contain
End & Tackle - Long Stick to A Gap
End - B gap blitz
Tackle - Jap then loop to B gap
This is an America's Blitz variation. The twist action of the long stick DT with the looping zero technique creates an America's blitz effect on both sides of the formation.
Man Free with the rushers covering the RB if the RB attempts to block them.
The offense has the numbers (6 vs. 6) to block the rush.
The left side (blue) picks up the pressure exactly as expected. The right (red) side is where the breakdown occurs. The guard is expecting the Center to be occupied with the zero technique. The guard sets out the B gap rush threat (either the Tackle or Will). When the Tackle long sticks the OG doesn't know initially if he will get help from the Center.
The Center squeezes the protection to the long stick DT when the zero technique loops. The guard locks on the long stick and realizes too late he needs to redirect to the looping zero technique. By the time the guard reacts the looping zero technique is through the B gap and pressuring the QB.
The Titans found a create way to bring odd front pass rush from an even front personnel. The usage of the Zero and 5 tech on a twist that plays out like America's blitz is also creative. This concept is a good way to get the zero technique a better pass rush option. Often an odd front nose is forced to fight through a center from a head up alignment. The Center often has protection help from one or both of the guards. In that environment, pass rush opportunities can be tough to come by for a zero technique. Creating rush opportunities for the zero technique to use athleticism is a good change of pace from simply asking him to bull rush the mid-line and push the pocket.