There are a lot of folks, still, who think we will be running a 3-4. There are a lot of folks, still, who think we're rid of the Tampa 43 that Marinelli used.
Simply put, the front that Seattle began to use in 2010 is the same front that Monte Kiffin used on Tony Dungy's Tampa 2, just on steriods.
Compared to the old Tampa 2 front, rather than having a DE, 3T, 1T and DE, you have a Leo, a 3T, a 1T and a big end. Or maybe you have a big end, a 3T, a 1T and a big end. Or maybe you have a Leo, a 3T, a 1T, and a 1 gapping big end.
It's not uncommon for the DC to switch out player roles on a game to game basis.
So what's a big end and what's a Leo? Big end is the end on the strong side of the formation. Leo is on the weak side. According to SI, an ideal two gapping big end is 280-295 pounds, 20 pounds lighter than a 3-4 DE. Leos can be regular 43 DEs, but because they are weak side, successful Leos can be lighter. And they can be hands in the dirt or 2 point stance, according to what they prefer.
The base therefore is a 4-3 under where 1/2 of the defense is using 3-4 techniques and the other half (the weak side half) is using 4-3 techniques.
But on a game to game basis, it doesn't have to be that.
In 2010, when they came up with this, they had to deal with Seattle's then horrible run defense. And it worked out of the box. If you want specific links, I can DM you my wikipedia draft..
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