Castillo, of course, was replaced last week by secondary coach Todd Bowles.
"We're going to get some unscouted looks, I'm sure of that," Atlanta coach Mike Smith said. "We're not anticipating that they're going to change from a 4-3 to a 3-4. But the way the game is going to be called may be different . . . or it may not."
Bowles has been an NFL defensive assistant since 2000, but he has never been a coordinator. He was the Dolphins' interim head coach at the end of last season and went 2-1 after Tony Sparano was fired.
"I think in what I call situational football - the third-down plays, the red-zone plays, the plays that really make a difference in a game - I'm sure are going to have a little different philosophy with coach Bowles," Smith said.
Atlanta wide receivers coach Terry Robiskie and Bowles were on the Cleveland staff from 2001-03.
"A couple of guys on our staff are familiar with coach Bowles," Smith concluded, " . . . although not as a defensive coordinator and calling a game."
A victory on Sunday would make Mike Smith the Falcons' all-time winningest coach. Smith is 49-21 since 2008. He is tied with Dan Reeves, who went 49-59-1 from 1997-03. Reeves brought the Falcons to their only Super Bowl, a loss to the Broncos following the 1998 season . . .
Former Eagle Asante Samuel had his first interception as a Falcon 2 weeks ago, scoring on a crucial 79-yard return in the fourth quarter of a 23-20 win over the Raiders. Samuel played for the Eagles from 2009-11 and has assisted in the game-planning for this week. "Asante can give us some insight on the roster, that's probably the biggest thing," Smith said. "He's practiced against those guys. He's a very intelligent football player" . . .
Atlanta (6-0) is the NFL's last undefeated team. Like the Eagles, they had a bye last week. The Eagles are 13-0 coming off a bye under Andy Reid. Atlanta is 3-1 under Smith, with wins each of the last 3 years.