Some of the pieces were already here – Fletcher Cox and Brandon Graham up front, a linebacker corps that returned intact, and a safety duo of Malcolm Jenkins and Rodney McLeod that only figured to improve. Otherwise, as the Eagles entered Training Camp in late July, there were questions about the defense.
Who would, for example, step up at what would be a very inexperienced cornerback position on both sides? How would it work at one defensive end position, where the Eagles looked to replace Connor Barwin? And inside, next to Cox, Tim Jernigan was here via trade but what would he bring to the table?
"I thought we were going to be good," linebacker Mychal Kendricks said. "Why? Because we prepare well and we have a bunch of good players. We mesh well. We work every darn day. That's real talk. You've got no one complaining about our work ethic and all the work we've put into this.
"It is only going to result in being good if you put in all the work we've put in, so there's that. It's our second year (in the Jim Schwartz scheme) so we've been able to focus on different aspects of our game."
What have the Eagles done defensively? They've survived a rash of injuries – middle linebacker Jordan Hicks is gone for the season, cornerback Ronald Darby hasn't played since Week 1, defensive tackle Fletcher Cox missed two games, and safety Rodney McLeod missed a game and a half – and they've continued to play with great energy and relentless pursuit.
Sunday's game against the Denver Broncos is being billed as a battle between the Broncos' "No-Fly Zone" defense and the Eagles' high-powered offense, but the Eagles' D can put its numbers up with pride in this game, too.
The Eagles lead the league in run defense, allowing 70.4 yards per game. They've averaged 1.8 takeaways per game, ranking seventh in the NFL. While the Broncos' defense has allowed opposing offenses a paltry 25 percent conversion rate on third down to top the NFL, the Eagles rank third at 31 percent. Where Denver has permitted an average of only 14.6 first downs per game (first in NFL), the Eagles have allowed only 17.9 first downs per game to rank seventh in the NFL.
But, shhhhhhhhhhhh, says Cox. It's OK that nobody is talking up the Eagles' defense.
"We need to stay underrated," he said. "This group we've got right now is just so humble. We're focused on what we're doing. The big plays are going around. It's not just one person making big plays. It's multiple guys. We've got that type of vibe, and it's special that guys are rallying around each other.
"As long as we keep grinding it out, we'll pick up our heads at the end of the year and see where we're at."
The team has improved, despite all the injuries in the secondary, its big plays allowed. There have been 21 passing plays of 20-plus yards allowed in eight games, a manageable number. The defense has taken the football away 14 times, leading to 54 Eagles points scored.
The challenge on Sunday is stopping a good Denver running game and to keep an explosive receiving group under wraps. Getting after starting quarterback Brock Osweiler is a key, of course, and the Eagles have been excellent at pushing the pocket and forcing quarterbacks off their spot.
"That's what we do," Graham said. "We need to go out and play our game. We need to play smart football and get after them. This is nice, what we're doing, especially with the injuries that we've had. I still feel that we're getting a lot stronger. It's a credit to how we practice and how much energy we bring.
has become a productive starter opposite Graham at defensive end, and the depth on the edges has been plentiful with Chris Long and Derek Barnett playing well in reserve roles. Jernigan and Cox have teamed perfectly at tackle, with Beau Allen as the primary reserve.
Kendricks, whose playing time diminished in recent seasons, has emerged as a key player in the defense and is now playing a more prominent role in coverage with Hicks out. Strongside linebacker Nigel Bradham is playing at an All-Pro level.
In the secondary, Jalen Mills has made a huge jump in his second season. Patrick Robinson, a throw-in free agent signee, has played very well at cornerback. Rookie Rasul Douglas has done a nice job taking big-time reps in Darby's absence.
The versatility of the safeties has paid dividends, with Malcolm Jenkins playing safety, nickel cornerback, and now dime linebacker with Hicks lost for the season, and veteran Corey Graham, another summertime free agent addition, has made the most of his reps at safety. He knows the scheme and he's always in the right position to make plays.
Added up, the defense has made itself into something formidable eight games into the year.
"The thing is, it's about what you do next in this league," Jenkins said. "We're just worried about what we're doing. We just want to keep this thing rolling the way it's been going this year. That's our only focus."