A 3-4 Eagle defensive front looks almost identical to a base 3-4 front however there are some subtle changes. The player lining up in the traditional defensive tackle or nose tackle spot in a 3-4 Eagle is actually a linebacker, making this defense into a 3-4 front with 5 linebackers on the field. Every other player has the same responsibilities as they would have had in a basic 3-4 but the offense is forced to adjust because of the smaller, quicker player playing inside against the interior of the offensive line.
By placing a fifth linebacker onto the field a level of versatility and unpredictability is introduced. 4 players will usually rush the passer however now they can come from many more directions than in a base 3-4 front while still maintaining good coverage at the same time. Gaining more speed allows for better coverage in general no matter the pass rush concept being used. Using this in stretches gives a completely different look that can force offenses to adjust which could also make it easier for the base package of the team.
Stopping the run becomes much more difficult when a linebacker is trying to take on the larger interior linemen. Also, if personnel is rotated through this nose linebacker position the offense can take advantage of the matchups presented to them pre-play allowing for a power run game to make this front very unsuccessful. Pass rushing versatility is acquired by sacrificing the strength of stopping the run which can be quite beneficial in small bursts of time throughout a game.