Both years that Golden has been here we've run a fair amount of 4-3 Under sets (I'm fairly sure it's the most common used defense for us against base offenses). Eddie Johnson and Armbrister were consistently playing on the line over the TE. In 3 or more receivers (or any twin sets really), we'd walk the WLB out over him and go to a more traditional 4-3 look (which would really look like more of a 4-2-5 look because the LB was so far out.
But for the Under look, at least last season, usually (and usually might not even be the right word, as guys played lots of different spots), Eddie was at Sam, Gaines at Mike, Denzel at Will, Chick at SDE, Green at weakside end, and then whatever healthy body we could find at the DT spots (though late it was Pierre at the 3 and Porter at the shaded). It's not an ideal set, because you'd like someone a little bigger than Chick at the 5 tech (Hamilton/Kamalu project there very well, though Chick can do it effectively in spurts), and you'd like someone more athletic at the weakside spot (coughAQMcough). With the body types they've been recruiting the Under/3-4 variations definitely seem to fit extremely well. There were times last season where the defense would come out in a straight 3-4 look, and there were also times they would be in the Under set and Green would stand up and shift out a bit to give a 3-4 look.
I really like the Under set because of two main reasons. First, you can disguise a lot of what you do, while also being in really good initial position to defend different looks. Having 5 guys on the line really helps with gap control and edge control, and with the way the DL is set up you can keep your LBs free to run. You can also bring either safety down in the box and still be able to run any coverage and blitz scheme out of the defense (if you have a good enough safety, which I think we do with Deon and eventually Jamal) while having 8 guys in the box to help against the run, or cover the slot with a DB instead of a backer. The second reason, is because you can fit a lot of different types of players in there and also mask a lot of issues (not all, as there are no schemes that can hide ****** DTs). The 5 tech doesn't have to be much of a pass rusher at all, the inside backers don't have to be huge because they're generally protected with good DT play. It does however puts a lot of pressure on the Sam though because they have to be pretty versatile (or you have to play multiple guys at the position, which I think we'll see with Figs/Armbrister/McCord).
It can be a complicated defense but you can keep it simple coverage wise, but the more comfortable the defense is adjusting to the offense the more effecient the defense will be.
All that said, the scheme doesn't matter one bit if you're running weak, inexperienced, untalented players out there, which we saw a lot of the past two seasons. Don't think we'll see that this season.
