Webster's definition of "feared" is "an unpleasant often strong emotion caused by anticipation or awareness of danger."
The first reaction when you see the phrase "a feared defense" may be to assume a playmaking defense. This is a defense that causes a lot of turnovers. This is a defense that can stop the run.
That's not the kind of fear that should be a priority for Philadelphia.
Offenses should come in to a matchup against the Eagles knowing that they're going to need an extra ice bath on the following day. Every Eagles opponent should give a postgame press conference talking about how the previous three hours were a "war."
This mentality has nothing to do with physical skill. It's a characteristic that can be developed in every player. Once it is, the transformation that follows can be incredible.
When you are tougher than the opponent, you want it more. It can be demoralizing and fatiguing for an opponent. Because of that, plays are made.
The defensive line begins to win more battles. When the defensive line wins more battles, the secondary benefits from a pressured quarterback. The list can go on and on.
By introducing a mentality of physicality like no one has ever seen, the Eagles can raise their level of play without even changing personnel (hopefully, they will do both).
Take it from the two teams competing for this year's Super Bowl; defense wins championships.