"All you can do is tell you the truth," Reid said Tuesday. "I've been questioned on every decision whether somebody else made it for me or didn't make it for me. That's not what this is about at all."
The decision was Reid's and Reid's alone. Owner Jeffrey Lurie hammered that point home a few hours later when he said he had nothing to do with Castillo's promotion in the first place.
Lurie seldom gets involved in coaching decisions, but it was a further distancing from his longtime coach. Last Sunday, Reid was five minutes away from a 4-2 record heading into the bye. A week later, at 3-3, he is on an island with presumably 10 games left to save his job.
In the middle of what was surely one of Reid's worst professional weeks, the Northampton County District Attorney's Office announced that Garrett Reid's Aug. 5 death was due to an accidental heroin overdose.
Here is a look back at five days that shook Reid's world:
Sunday. When you coach in the NFL for 14 seasons, you're going to have more than a handful of stinkers. But the stench from the 26-23 overtime loss to the Lions will linger if the Eagles can't turn this season around. During the postgame presser, Reid reverted to form, grumbling out answers during a terse, three-minute interview.
Calls for the end of his tenure, meanwhile, reached a crescendo, with even the most loyal of Reid supporters taking to talk radio; the Internet; and the brisk, moonless night to voice their ire.
Monday. A day later, after watching his team's collapse on film, Reid offered a strong critique. He did not question Castillo's late-game play-calling, however, and he sternly rebutted cornerback Nnamdi Asomugha's claim that the Eagles altered their defense down the stretch. Still, he offered tepid support when asked if Castillo would remain his play-caller.
"There's ways of buying time in this business, where you can think," Reid said. "Mondays are pretty crazy. You want to make sure you step back a little bit."
By the early evening he had come to the conclusion that Castillo, who once said he would take a bullet for Reid, should go. Later that night he called his longtime assistant into his office and fired him.
Tuesday. Before he told Castillo, Reid said he went to Lurie with his decision.
"Jeffrey was good," Reid said. "He was not too high, not too low. He was good with it. He understands."
Still, Lurie would say the following day that, in essence, Castillo's failure was Reid's failure. "That's not Juan's fault that he was put in that position too early," Lurie told the Philadelphia Daily News.
Before Reid met with reporters, an Eagles employee told the coach to be prepared for pointed questions about his future. They came like rapid fire. The Reid that became more accommodating during the offseason, not the defiant one from the previous two days, answered every one.
He kept going. It was a rare sight, Reid taking questions on the second floor of the NovaCare Complex. At one point, just as he was talking about his relationship with Castillo, new defensive coordinator Todd Bowles walked by.
"Bad timing right there," Reid said.
Wednesday. Reid had said replacing Castillo with Bowles was just one of the moves he would make. He continued his evaluations a day later, as he said he would, tearing the team apart bit by bit.
At some point, he had decided that his best course would be to stick with Michael Vick as his quarterback and offensive coordinator Marty Mornhinweg as his play-caller. A day later, team sources told The Inquirer that both were staying put.
Thursday. A reminder that Reid was coaching only two months after his son had died at training camp came in the form of released toxicology reports that said heroin ended Garrett Reid's long battle with addiction.
"These results sadly confirmed what we had expected all along," the Reid family said in a statement.
Police said they discovered 47 syringes and 64 needles in a gym bag along with 19 vials of an unknown liquid in Reid's Lehigh University dorm room.
Friday. The Eagles had yet to respond to a request for Lurie to comment on the drug paraphernalia found around his team.
Reid, meanwhile, keeps his eyes only on that next game, even if the perception is that the walls are falling in on him.
"You can't worry about that," Reid said just after he exited the elevator. "I got to do what I think is right, right now."
Contact Jeff McLane at firstname.lastname@example.org, or follow on Twitter @Jeff_McLane.