This year, he will coach there as the Eagles' defensive coordinator.
The beleaguered, scapegoated defensive coordinator.
Castillo took over the defense this season. He was given two Pro Bowl cornerbacks, Nnamdi Asomugha and Dominique Rodgers-Cromartie, Pro Bowl end Jason Babin, stud tackle Cullen Jenkins and revered defensive line coach Jim Washburn.
The Eagles then blew five fourth-quarter leads, which sunk them to 6-8, needing a win Saturday night to remain relevant.
It is not the homecoming Castillo envisioned. And, so, he has not thought about it.
"I really haven't had much time to think about going home," Castillo said. He has been figuring out which plays Dallas will run, and deciding "what plays you actually master defending in practice."
His aunt and his sisters might come. He doesn't know for sure. His uncle is too sick to travel, but his in-laws, from Kingsville, should be there.
He hasn't even heard from the buddies he played with at Texas A & M in Kingsville. They are leaving him alone, he said, because they understand the rigors of preparing for such a game.
"They understand: This is all focus," Castillo said appreciatively. "You know you've treated people right. You know you've helped them in their lives. It lets you know you're doing the right things.
"Sometimes, it takes a little longer. Your faith gets tested."
The veil for that metaphor is too thin to acknowledge.
Castillo, who never was a defensive coordinator beyond high school, shouldered much of the blame for the Eagles' 3-6 start. His defense, tentative and confused, leaked away those five late leads.
Head coach Andy Reid was pilloried for his decision to switch Castillo from offensive line to defensive coordinator. Reid constantly fielded questions about Castillo's job security.
The Birds have since gone 3-2, the losses coming without the services of quarterback Michael Vick and receiver Jeremy Maclin. Castillo's defense held the Giants, Dolphins and Jets to fewer than 20 points apiece in the wins.
The Eagles rank 10th in the NFL in yards surrendered, ninth on third-down conversions and first in sacks per pass play.
But they are 19th in points allowed, largely because they rank 30th in red-zone defense.
These are not bragging stats.
Offensive innovations and Houston's historical sideshow aside, in Texas, particularly in Dallas, effective defense equates to winning football. It is a visceral thing there.
Well, Castillo isn't the bragging type.
But he does have his pride.
His players know it.
"It would be a lot better for him," said Juqua Parker, a native Texan and one of the longest-tenured Eagles.
"That would be sweet," said Joselio Hanson, who starred at Texas Tech and owns a home in Fort Worth.
Dallas has the No. 6 offense in the league. Castillo and Co. shut it out for the first 47 minutes of their Oct. 30 rout.
A repeat performance surely would make the trip home a little less humbling. Castillo agreed.
"You want to do well," Castillo said, "so you don't let the people down who are pulling for you."
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