[Buzzbee]

I have absolutely NOTHING to back this up, but I wonder if the success of LB's such as Lawrence Taylor, Mike Singletary and other such "high profile" linebackers has driven up the salaries of LB's to where "swapping out" a cheaper DL make financial sense.

I don't think this is the case, but the thought has crossed my mind.

In my opinion, it all centers around having a pass rush. The pass has been used much more in recent years than in decades past. As a result, defenses are focusing more on putting pressure on the QB. So, adding a DL gives you more people up front for the OL to deal with. It also allows the DE's to shift more toward pass rush specialists since you have two big DT's instead of one.

I'm also curious if the move from a traditional I-formation to more of a pro set, or even the singleback sets has resulted in less need for 4 linebackers (operating on the assumption that LB's generally have cover responsibility for RB's/FB's).

Just my $0.02.