"In the first half, we couldn't get them into third-down [situations]," defensive coordinator Bill Davis said. "In the second half, we were getting to third down, but weren't making the plays we needed to make to get off the field and give the ball back to our offense."
In their last 10 games last season after Andy Reid fired his defensive coordinator, Juan Castillo, and replaced him with secondary coach Todd Bowles, the Eagles were atrocious against the pass, particularly on third down. They had a 132.3 opponent passer rating on third down in those final 10 games. Gave up eight touchdowns and had no interceptions. Opponents had a .653 third-down completion percentage.
They made a number of personnel changes both up front and in the secondary to try to improve a pass defense that gave up a franchise-record 33 touchdown passes last year.
But it's going to take time to get this defense to where it wants to be.
The Eagles are woefully thin in the secondary, and that showed yesterday. They were missing one corner, Bradley Fletcher, who was out with a concussion. Another, Brandon Hughes, who was coming off a broken hand, suffered a hamstring injury in the first half. Yet another, rookie seventh-rounder Jordan Poyer, played so poorly against the Redskins in Week 1 that Davis wasn't even confident enough to put him in the game.
That forced the defense to stay in its base defense most of the second half against the Chargers' "11" personnel (three wide receiver, one tight end and one running back) and use safety Patrick Chung to cover slot receivers.
Rivers made mincemeat of the secondary. Completed one big play after another against them, many on third down.
On the Chargers' first scoring drive of the second half, he completed an 18-yard pass to rookie Keenan Allen on third-and-8, a 21-yarder to Eddie Royal on third-and-7 and finally, a 24-yard touchdown pass to a wide-open Royal on a third-and-10 play.
Two San Diego possessions later, Chung was called for defensive holding on a third-and-4, Rivers completed a 7-yard pass for a first down to tight end Antonio Gates on another third-and-4, a 16-yarder to Allen on third-and-7 and a 12-yarder to Royal on third-and-6.
It pretty much went like that the entire second half, with Rivers and Royal combining on a 15-yard screen pass for a touchdown with 3:11 left in the fourth quarter that gave the Chargers a 30-27 lead.
"We made a lot of mistakes defensively,'' Davis said. "No more than last week [against Washington]. They just executed better."
Throw in the fourth quarter of the Washington game, when Robert Griffin III completed 15 of 21 passes for 169 yards and two touchdowns, and opposing quarterbacks have completed 75 percent of their passes, averaged 8.6 yards per attempt and thrown five touchdown passes against the Eagles in the last five quarters.
"We threw everything at [Rivers]," Davis said. "Four-man rush, five-man rush, six-man rush, everything. We tried to change it up and bluffed blitzes and fell back. Philip had a better day than we did."
The Eagles' secondary isn't good enough to survive by itself without the aid of a consistent pass rush, particularly when one of their starting corners is out.
There is no shutdown corner. There is no playmaking safety. Both Chung and Nate Allen played poorly. So did Cary Williams, who had been one of the stars of the Week 1 win over the Redskins.
"It's a testament to those guys and their preparation,'' Williams said of the Chargers. "Sometimes you're going to come up against great quarterbacks."
The problem is, Rivers hardly is the only good quarterback on the Eagles' dance card. Looming ahead are the likes of the Manning brothers and Aaron Rodgers and Tony Romo and Matthew Stafford and Jay Cutler and Griffin, who won't be rusty the next time the Eagles face him.
Williams and the Eagles' other corner, Brandon Boykin, said Rivers seemed to know exactly what the defense was going to do.
"He just seemed to know everything we were trying to throw at him today,'' Williams said. "He was calling things out. He's a veteran guy. He's savvy. He caught us in bad situations. He used those matchups against us. He was able to capitalize.
"They just were able to understand what we were trying to do as a defense. They did a great job in their preparation. A great job in their game plan. They understood some of our calls, or whatever was going on. It looked like he knew exactly what [linebacker] DeMeco [Ryans] was calling, to a degree. He knew exactly what we were in, to a degree.
"It was unfortunate. Sometimes you get outwitted. Sometimes you get outplayed. I think today was one of those days."
Said Boykin: "Rivers is a great quarterback. You've got to give him credit. A lot of times, he knew what we were in. He would check and they would do something different. We've got to lock on our men when he has time, and we didn't do that very well.
"We've got to be a lot better. And we will. It's just the second game. We're going to look at the film and make corrections. We take pride in our defense. We weren't happy with the way we finished that first game. I thought we played better in the first half today and did some good things. But the [second-half] completions on third down really killed us."
Buckle your seat belts. It's going to be a bumpy ride.
On Twitter: @Pdomo