Despite a first season for Castillo as defensive coordinator that was more Herman's Hermits than Rolling Stones, Eagles coach Andy Reid decided to bring him back with his band minus one piece.
Defensive backs coach Johnnie Lynn was jettisoned and replaced by Todd Bowles, although Reid acknowledged in January that he had approached Steve Spagnuolo about a job that most certainly would have given him some authority over the defense - not exactly a ringing endorsement of Castillo.
And yet Reid ultimately stayed with the loyal Castillo, believing that the advances the defense made late last season would carry over with a full offseason.
"Last year's gone," Castillo said Tuesday as Eagles defensive assistants met with reporters at the NovaCare Complex. "It's about this year. It's about us getting off to a good start, and starting where we left off last year."
The Eagles won four straight to end the season, and Castillo's unit - specifically the back seven - seemed to finally grasp the intricacies of playing with a wide-nine defensive front. Still, the changes made this offseason were at linebacker and in the secondary.
Asante Samuel was traded to Atlanta, and Dominique Rodgers-Cromartie will move to left cornerback. Rookie Brandon Boykin also is expected to vie with Joselio Hanson for the ever-important nickel position.
At linebacker, DeMeco Ryans was acquired in a trade with Houston and will man the middle, and rookie Mychal Kendricks will be given every chance to win the strong-side spot.
Schematically, the tinkering will be done in the back seven, too, although it's difficult to predict how much change will take place when the games are played. Nnamdi Asomugha and Rodgers-Cromartie are expected to play more man-press cover. Castillo, despite blitzing significantly less than his predecessors, is expected to send more extra rushers, with Ryans and Kendricks skilled in that area.
Washburn's wide nine, which became a catchphrase for all that was wrong with the defense last season, will remain intact.
"No. 1, it's not . . . Jim Washburn's so-and-so. It's Eagles," Washburn said. "Andy wanted to run this defense, and Jim Washburn got very little to do with it, really."
The wide nine, on its own, was successful. The Eagles' front four led the NFL with 50 sacks. Reid gave Washburn more ammunition when he drafted defensive tackle Fletcher Cox in the first round and defensive end Vinny Curry a round later.
Offsetting the success of the wide nine was the need to ask the linebackers and safeties to take on additional run-stopping responsibilities. Castillo, too, had to learn a scheme that he rarely had seen as an offensive line coach.
"We all had to get used to everything; it wasn't just Juan," Washburn said. "It was all of us. It was a learning deal."
Castillo, during spring practices this month, has been working mostly with the linebackers and defensive backs as Washburn drills his linemen. The perception has been that the defensive coordinator leaves the front four almost exclusively to his position coach.
"He probably leans in more to the skill guys," safeties coach Mike Zordich said of Castillo, "but he's still very involved in the front four."
Bowles was brought in to help Castillo in the secondary. He was an assistant head coach with the Miami Dolphins and has interviewed for defensive coordinator positions. The Eagles had requested permission to talk with Bowles last year for the vacancy that eventually was filled by Castillo.
"You want to have the best staff in the NFL," Castillo said. "I think it started when Jim Johnson was here. Jim Johnson, I think, had four guys that went on to become head coaches."
Castillo, as Washburn said, has never appeared to be preoccupied with such aspirations. On the surface, he hasn't changed much this offseason. He still wakes up for work at 4 a.m. He still does his best to keep his plans secret. And he's still a big ball of positivity.
Asked what he thought was the biggest thing he learned last season, Castillo answered in true form, "That when you work hard, and you believe in something, and you don't change no matter, that good things do happen."
Contact Jeff McLane at 215-854-4745, firstname.lastname@example.org, or on Twitter @Jeff_McLane.