PHILADELPHIA -- All that progress the Philadelphia Eagles' defense made over two months vanished in one day.
It doesn't mean they're back to the beginning.
Led by Matt Cassel and a third-string running back making his first career start, the Minnesota Vikings scored 48 points against Philadelphia on Sunday.
Cassel exposed the secondary with deep throws, connecting with veteran Greg Jennings 11 times for 163 yards on his way to a 382-yard passing performance.
The Eagles (8-6) hadn't allowed more than 21 points in the previous nine games since Peyton Manning and the Denver Broncos scored 52 against them — 38 off the defense and 14 off special teams — in Week 4.
"I think it was a bad day, but I think you always have your strengths and weaknesses," defensive coordinator Billy Davis said Tuesday. "We've said all along we've got so much more to do. This is Year One. We have had a lot of success that probably was unexpected.
"But the weaknesses, nothing has really changed. We just continue to try to get better and better as we go. We did walk into a bad game, a good Minnesota team. We have to learn from it and respond to it. I believe they will respond in the right way."
The defense faced a team missing its best offensive player, reigning NFL MVP Adrian Peterson, and his backup, Toby Gerhart. But Matt Asiata ran for three touchdowns in their absence.
Cassel took advantage of a depleted secondary with six pass plays of 20-plus yards, and several third-down conversions. Cornerbacks Cary Williams and Bradley Fletcher struggled along with safeties Patrick Chung and Nate Allen.
The Eagles sorely missed rookie safety Earl Wolff, who didn't play because of a knee injury. Nickel cornerback Brandon Boykin sustained a concussion during the game.
"I have never coached in a game where we didn't have multiple errors. I don't think anybody has. It just doesn't happen," Davis said.
"There's always the little things you have to tighten up and get better. When you lose, a lot of times the mistakes you make, they're found. You always have to correct them. You have to be really tight in your coverage and your assignment and doing your job."
Things won't get easier for the defense this week against Jay Cutler and the Chicago Bears (8-6). Brandon Marshall and Alshon Jeffery have combined for 170 receptions, 2,450 yards receiving and 17 TDs. Matt Forte has 1,200 yards rushing and 522 more receiving on 66 catches, and he's scored nine TDs combined.
"It's a huge challenge for us," Davis said. "Chicago might be one of the most talented offenses we face. Big, physical Pro Bowl receivers, two of them. They have a tight end who is a big, athletic passing tight end.
"The running back is as rounded as any running back we've faced. His pass protection is great. He runs the ball well. He catches out of the backfield well. The offensive line is young on one side, but it's getting better and better as we go. The quarterback can make all the throws. This is overall our biggest test."
The good news for the Eagles is the game might not mean much in the standings other than playoff seeding, a No. 3 or 4. They have a one-game lead over Dallas (7-7) in the NFC East.
If the Cowboys beat the Redskins in an earlier game, the division winner will be decided when the Eagles play at Dallas next week. If the Cowboys lose, however, the Eagles can clinch with a victory over Chicago.