A Nickel defense is when the defense substitutes an extra defensive back for either a linebacker or a defensive lineman. The Nickel back is usually the 3rd corner. It essentially turns the 3-4 into more of a 4-2-5 or a 3-3-5 look.
In some games, the defense will open in a nickel because they are facing a pass-happy team like the Patriots or Chargers, or scouting and tendencies dictate that the offense opens with a pass.
Before moving on to Cover 4, 5 & 6, it’s necessary to take a look at nickle and dime formations so those articles can reference back here. Same for Cover 3.
In a standard Cover 2 formation (what Denver usually runs), there are four defensive backs: two safeties and two cornerbacks usually playing man coverage.
On some plays, Joe Woods, the Defensive Coordinator, may think he’s looking at a pass heavy play with four receivers/TE’s, so he may want to add another DB. If he adds a 6th, this is called a dime because it’s the next coin up.
There are many options that can be used dependant on the play. First, if someone is added, someone else is coming off the field. This is where things get complicated. If he’s sure it’s a pass play because there are three WR or say a 12 set (1 RB, 2 TEs, 2 WR ), he may remove the Nose Tackle, move the Defensive ends closer and spread the linebackers out, while putting the nickle behind the LB’s and between the safeties.
Some teams like to use a nickel as their main formation because either they don’t have three good LBs or a good FS. Maybe their NT stinks. Or their CB’s aren’t great so they need an extra body. Denver used to only use it when facing a pass happy offense.
In 2017, it was used a lot more because losing Shane Ray meant the LB unit was weaker and therefore, so was rushing the passer. When you give teams more time to throw, they generally will. This necessitated more nickel.
If you need an example of the Broncos living in Nickel, you can look to the Green Bay game from 2015. It was the regular season game where they broke Aaron Rodgers, although Rodgers completed 63% of his passes, he only generated 77 yards passing. A net of 50 yards when you take into account the sacks. Chris Harris Jr., Bradley Roby and Aqib Talib were each on the field 91%+. It is one of the best defensive performances in the history of the NFL.
Another fine example of this was the 2015 AFC Championship game when they gave Tom Brady the same treatment.
When a QB is on the top of his game, he can punish a Nickel defense with a mix of runs and passes with either the 12 set mentioned above or a 11 set (1RB, 1 TE, 3 WR). If an offense has the ability to run and throw from those formations, then it’s generally a long day for the defense.
A dime defense is a formation in which a 6th defensive back is inserted into the defense and in this case, more times than not, it is a linebacker coming off the field. When Coach Woods decides to add the 6th DB this is called a dime because it’s the next coin up and another LB/DL head to the sideline.
One thing that the Dime allows, is to mix zone/man more, so some of the 6 DB’s might be employing Zones and some might be man to man.
When Broncos run their Dime, and at times their Nickel, they drop Von Miller into more of a pure rushing/defensive end position so he can generate a pass rush to disrupt the Quarterback into making a mistake.
It looks as if they are running a 4-man front because basically they are. There are times that a 3-4 is more of a 4-3 front from a conceptual basis. However, when that 6th DB is added, a linebacker is coming off.
If a proficient and dynamic OC can catch a defense in the Dime, they can really do some damage in running a no-huddle scheme. That can force the defense to use a timeout to stop the madness. They can easily take advantage of the lack of the missing run support and move the ball down the field. It’s all about the best perceived match-up based on scouting and tendencies.