The problem with the Eagles pass defense Sunday was not only that it failed to stop the Chargers in a 33-30 loss. It was that San Diego quarterback Philip Rivers approached the line of scrimmage, saw how the Eagles were prepared to defend him, and often had an answer for what the defense presented.

A day after the game, the Eagles continued lauding Rivers, a four-time Pro Bowler who completed 76.6 percent of his passes for 419 yards and three touchdowns. Coach Chip Kelly said that the Chargers "put the game in his hands" and that Rivers called plays at the line of scrimmage based on the Eagles defense.

"That's part of what their whole package was," Kelly said. "They'd get up, take a look, then come back. Sometimes they checked, we checked, and then they checked again."

Defensive players spoke after the game about Rivers' mastery of the Eagles' defense. Cornerback Cary Williams said the Eagles were "outwitted" and "outplayed."

Kelly said it takes a "certain type of quarterback" to play the way the Chargers did. The problem for the Eagles is that Rivers is not the only quarterback on their schedule who can do that.

Nine of the Eagles' 14 remaining games feature an opposing quarterback who has reached the Pro Bowl. That group includes Peyton Manning, Aaron Rodgers, and Eli Manning (twice). The next test for the Eagles is Thursday night against Alex Smith and the Kansas City Chiefs.

"I understand, and we do, too, but it's the second game," cornerback Brandon Boykin said. "I'm going to adjust, coaches are going to adjust. The game plan will get better. We'll figure out our techniques and get better at that. I don't think it'll be something that will prevent us from being successful."

The way to counteract a quarterback who is savvy at making calls at the line is to try to disguise the coverages and blitzes. That's what the Eagles did Sunday with little success.

Kelly said the risk comes if the quarterback snaps the ball early when the defense is in a disguise and is out of position. So the defense must approach the line in position for a play, then change as a disguise but be in position to change back.

"It's kind of a little chess game, and you see who can hold it longer until the play clock gets under five seconds and then show your real look," linebacker Connor Barwin said. "Obviously, [Rivers] kind of won that battle and got us to show our hand more often than not."

One difference in Sunday's game was the history that Chargers offensive coordinator Ken Whisenhunt had with Eagles defensive coordinator Bill Davis. Whisenhunt employed Davis as his defensive coordinator when he was the Cardinals' head coach, so he might have an understanding of how Davis likes to call a game and design coverages and blitzes.

Eagles players did not believe that was an issue. Kelly said he believes that Davis' terminology is different from what it was in Arizona.

"I know our defense spent a lot of time as a group putting together the defensive package, so there was a lot of influences from a lot of different places, from all those guys that were in the defensive room," Kelly said.

Still, the Eagles need to fix their pass defense. And they will need to do it with the players on the roster. It will help to get starting cornerback Bradley Fletcher back Thursday. Fletcher sat out the Chargers game with a concussion but returned to practice on Monday.

The Eagles remain in flux at safety, where Nate Allen is still a starter who splits time with Earl Wolff. The defensive backfield was an issue entering the season, and Sunday's poor performance only legitimized the preseason concern. It would help if the Eagles generate more of a pass rush, too.

Without elite personnel, though, the scheme must help the Eagles in games. They cannot afford quarterbacks' deciphering the defense before the play and dissecting it during the play.

"It's something we obviously looked at," Barwin said, "and won't let happen again."