In Washburn's scheme the Eagles front four lines up wide, creating space to use their speed off the snap but often leaving large gaps between linemen. Those holes allow offensive linemen to run free at linebackers when they're run-blocking instead of pass-protecting.
"You've got to know how to get off blocks," said linebacker Jamar Chaney. "You can't sit there and wrestle with a 300-pounder."
Linebacker Casey Matthews said the Eagles' line play works like this: "Right when the ball is snapped, they're off, and don't worry about the run or pass reads, just get up the field, because if it's a pass you've already shot off the line of scrimmage. If it's run, you should already be in the backfield."
The aggressive mentality can mean adjustments on the fly for the back seven. Each linebacker starts a play assigned to a specific gap, but if the linemen get into that hole instead, the linebackers change plans on the fly.
In other schemes defensive tackles have more responsibility for taking on blocks and leaving linebackers free.
"It's almost like we have to play off them because a lot of times they just keep their head down and go," Matthews said. "If they're in the B gap and they get washed to the A gap . . . we got to fill their gap."
He added, "We have to make them right."
Neither Matthews nor Chaney was complaining about the assignments, just explaining them. Each praised the new defense.
"It gives you an opportunity to attack and be aggressive," Matthews said. "It sounds hard, but it's not actually quite that hard."
Chaney said defensive line penetration can make running backs hesitate.
But the system is primarily aimed at disrupting passing games in a league where passing dominates. After the Eagles gave up 31 passing touchdowns in 2010, third most in the NFL, they needed a fix, particularly if they want to win a conference that includes Aaron Rodgers and Drew Brees. The two quarterbacks threw for a combined 731 yards in Thursday's NFL season opener.
"It allows the defensive ends to really get the type of rush that you want," said safety Kurt Coleman, who said he, too, has more run responsibility this year, particularly in the middle of the field as defensive ends and tackles line up wide.
But the preseason provided some glimpses of what could go wrong. With the Eagles' front four spread wide, the Steelers' Rashard Mendenhall hit them for 28 yards on six carries. On one play the line was so spread out that quarterback Ben Roethlisberger took a snap and simply ran forward untouched for 8 yards.
They are small samples, and preseason games aren't always great measuring sticks. But they represent concerns.
In the playoffs last season, the Eagles held Rodgers to 180 yards passing but gave up 123 yards to running back James Starks, allowing the Packers to control the game.
Last year the Eagles used big defensive tackles Mike Patterson and Antonio Dixon to plug the middle of the field. Now Cullen Jenkins, a better pass rusher, has replaced Dixon as a starter.
Defensive end Darryl Tapp said the linemen love the simple aggression Washburn has taught. But aggression can be turned against the defense with misdirection, draws, and trap plays.
"You've just got to react to the run," Tapp said. "Once we realize it's a run, that's when the calvary has to come."
The first test comes against the Rams and Steven Jackson, who has run for more than 1,000 yards six consecutive seasons.
The Eagles said they feel ready, but with seven defensive starters either new to the team or in new positions, they also say the defense isn't a finished product.
In interviews last week, six defensive players and Castillo each referred to a process of evolving during the season.
"Obviously it's not going to be the same in Week 10 as it is Week 1, but I think where we are right now is good enough to go out and dominate," cornerback Nnamdi Asomugha said.
With so many new parts and an abbreviated offseason to come together, Jenkins said there were more unknowns before the first game than usual.
"We're going to answer a lot of questions coming this Sunday," he said.
Contact staff writer Jonathan Tamari at 215-854-5214, firstname.lastname@example.org or @JonathanTamari on Twitter.