Gotcha, all I know is what I saw at the Navy game and the 3-4 just plain did not work.. Diaco may have switched schemes at some point.. but after halftime I was about 6 tall bud lights in after a pre-game and angry.. so my wits were not about me. I think I remember him saying he was gonna switch to the 4-3 for Army.. and that worked out well. I'd honestly have to study up on schematics to really get into the conversation this thread has created. I do like reading it, it's interesting.
All credit for this explanation goes to FightingIrish44 on the II board:
"We played a 3-4 Cover 4 vs. Navy. Unfortunately, I deleted the game and can’t look at exactly what went wrong. What I do know is the defense was unsound. I know this because of the game the Navy FB had. If you’re playing it correctly, the FB should rarely get the ball (only when they block it a certain way that makes the FB the carrier). We didn’t get beat because of a 3-4. The front doesn’t matter. What matters is execution. Like I said, I wish I still had the game on my DVR. I think part of the problem was the coaches gave the OLB’s and safeties predetermined assignments. So instead of reacting to how Navy blocked the play, which would determine the proper assignments, our OLB would play the pitch and the QB would cut inside him. That’s just an example that I recall. They also got us good with their unbalanced formation.
Vs Army, we played a 4-4. The base alignments were:
DE’s in 5 techs (outside shade of OT)
DT’s in 2i’s (inside shade of OG)
ILB’s in 30′s (outside shade of OG at depth)
OLB’s outside end man on line of scrimmage.
Safety run the alley to direction of flow
CB’s deep half (essentially man-to-man vs the WR.
This alignment takes away the midline option and forces the veer option (FB aiming point at guard).
The DT’s just plug the A gap all day long.
The DE’s were responsible for “squeezing” the down block of the OT. Then they tackled whatever threat was there (FB). Squeezing the down block allows the ILB to flow over the top.
ILB’s read flow and check their B gap. If open, attack and tackle the FB. If closed, which it usually was, scrape to the C gap and play QB. The OLB’s read the wing back to their side and reacted to his block. Maintain outside leverage and play pitch on wide blocks by wing backs. Squeeze down blocks by wing backs and play QB.
We executed pretty much flawlessly that game. It was beautiful. However, we changed the structure of our base defense’s. This is not generally a good idea, but was acceptable because we didn’t know how to stop Navy out of our base defenses. So don’t be surprised if we come out in a 3-4 Cover 4 vs. Navy and Air Force next year."
