We'll begin to find out Sunday if Reid's decision to cut Castillo and promote Todd Bowles will make any significant difference for a defense that seemed to always be at its worst when the plays meant the most under the former coordinator.
Thursday was another good day for April and offensive coordinator Marty Mornhinweg because they had units to coordinate for the team's Week 8 game against the unbeaten Atlanta Falcons.
Even though it was the defense that collapsed at crunch time in consecutive losses to Pittsburgh and Detroit, it's impossible to assign passing grades to either April's special teams or Mornhinweg's offense at this point of the season.
The Eagles rank in the bottom half in every major special-teams statistical category. They have been poor at returning kicks and atrocious at covering them. They are on their second punter this season, and their primary punt returner ranks 26th.
The Eagles have not been particularly good on special teams since John Harbaugh abandoned the role of coordinator after the 2006 season. It's hard to remember a spectacular special-teams play since DeSean Jackson's game-winning punt return in the Meadowlands two seasons ago.
April told some disturbing truths as he explained problems with punt returns so far this season. He said there are two problems: The primary one is that the Eagles do not get enough pressure on the punter. The secondary reason is that they do not prevent the other team from getting downfield.
Other than that, it's a well-oiled machine.
"We misjudged some of the fundamental stuff we did, and we weren't as fundamentally sound as we should have been going into the season," April said. "We're trying with every effort to whup the guy one-on-one through technique and through fundamentals."
More noticeable than the problems on special teams have been the offensive breakdowns that have left the Eagles with the 30th-ranked scoring offense in the NFL. Mornhinweg is in charge of that failing facet of the Eagles' game, but he and Reid are conjoined coaches connected by the same play-calling brain.
As long as Andy is around, so is Marty, which means they're both safe until owner Jeffrey Lurie decides his dream of a Super Bowl title is no longer possible with Reid in command.
The future of the head coach and the offensive coordinator will ride on the play of quarterback Michael Vick, a risky proposition that Mornhinweg seemed to fully understand as he tried to explain how the offense could be better coming out of the bye week.
"We have to flip that turnover ratio, that's the big thing," Mornhinweg said. "Let me make myself very clear, we have to play better in many instances. However, we flip that turnover ratio, and that takes care of an awful lot of things. That's the biggest key when you look at everything with fine detail. When you make it simple - if we flip the turnover ratio, it will take care of an awful lot of things."
You can disagree with particular play calls in certain situations by the offensive coordinator, but Mornhinweg's bottom-line review of the Eagles' offensive problems are right on target. The Eagles' 17 turnovers are the most in the NFC and second most in the NFL, and that's why they have the league's 30th-ranked scoring offense despite having the seventh-most yards.
Twelve of those 17 turnovers have come in the opposing team's territory. If each of those dozen possessions ended with field goals, the Eagles would have 36 more points this season. If six of the 12 had ended in touchdowns and the other six in field goals, the Eagles would be ranked eighth in the league in scoring offense.
Vick is responsible for nine of the 12 turnovers in the opposing team's territory and 13 turnovers overall.
The bad news for the Eagles is that the Falcons are fourth in the NFL and second in the NFC with 17 takeaways, which is a big reason they will come into Lincoln Financial Field as the league's only unbeaten team.
The worse news for the Eagles is that they do not seem to have any greater solution to this year's T.O. problem than the one that destroyed the team seven years ago. That's why a lot of really bad good days could lie ahead for April and the entire Eagles coaching staff.
Contact Bob Brookover at email@example.com, or follow on Twitter @brookob.