Twenty years ago, the term ‘3-4’ defense versus ‘4-3’ had stark differences. A 4-3 defensive end was very different than a 3-4 outside linebacker. The Pittsburgh Steelers used this to their advantage in the 1990s when they were the only team running a 3-4, because these so-called “tweener” players, not big enough to play DE, but too big to play linebacker, weren’t in demand by any other team but were perfectly suited for the 3-4. The Steelers were able to draft them later than their talent merited because there was no competition for their services. Joey Porter was a third-round pick, and Greg Lloyd was a sixth. But football is ever evolving, and as more teams switched to the 3-4, competition for those bigger edge rushers intensified, and the Steelers lost their advantage.
This evolution in defensive formations and player roles has accelerated in the last few years with rule changes favoring passing even more than before. Teams now spend the bulk of their snaps in a nickel formation, with four to five players on the line, one to two off ball linebackers, and five defensive backs. Some teams spend more time in a dime formation with six defensive backs than in their “base” formation with only four defensive backs. As such, old names for positions are being replaced. Yet, even as the distinctions between a 3-4 defense and a 4-3 defense blurs and merges, the use of designating a team’s defense as a 3-4 or 4-3 carries on, with significant and outsized effects for fantasy football.