Why is a 4-2-5 defense named as such?

Question

I was watching a Bleacher Report video. In the video breaking down the TAMU-SC opener game, the narrator said, "Thanks to the abundance of linebacking talent, [SC] are looking to move to more of a 3-4 than their traditional 4-2-5."

I understand the 3-4, but in looking at the 4-2-5 defense online, I can't make heads or tails out of why a defense would be called 4-2-5.

Bonus points for anyone who can explain this defensive numbering system in a way so that the concept can be applied to other formations.

Answer 1

For the defense, there are three zones: the line (ends and tackles), behind the line (linebackers) and the backfield (cornerbacks and safetys.) The x-y-z defenese refers to the number of men on the line, linebackers and backfield respectively, that is 4-2-5.

The confusion arises from the fact that the "3-4" defense is really the 3-4-(4), and likewise the "4-3" is really the 4-3-(4).That is to say the the "4" is omitted in the above defensive descriptions because that is a normal number of backfielders.

The 4-2-5 is written out as such because 5 is an unusual number of backfielders. This formation is used in college football against a "passing" team, and in "pro" football in "sure" (e.g. third and long) passing situations. The defense is saying that they don't mind giving up say, a five yard run in order to stop the pass.

There were a bunch of older formations, such as the 6-2-3, or the 5-3-3, until these line-oriented defenses got beaten by passes. The only thing they have in common is that x+y+z all add up to 11, the number of players each team has on the football field.

Answer 2

Generally in defensive formations they are listed "downline men - linebackers - defensive backs*" (*defensive backs are not usually listed, 4-2-5 is an exception).

So in 4-2-5, you have 4 down linemen, 2 linebackers and 5 defensive backs in this setup. This is a setup where you are expecting the pass, and have confidence in your linemen to get pressure on the quarter back.

A 4-2-5 is mostly regularly played in college where spread offenses are very common and you need more defensive backs to combat the prolific passing game. However, on long third down situations, this is also a fairly common defense in pro football. For instance, one version of this formation is the one you will hear referred to as the "Nickel Package.", in which you have 3 corner backs and 2 safeties. However, there are other version of this defense played in the NFL where you will have 3 safeties and 2 corners.

While it can be viable as an every down defense in college it is relegated to situational football in pro defenses in favor of more traditional 3-4 or 4-3 setups.