The Washington Redskins studied the offenses that Chip Kelly had coached in college at Oregon. They talked before their Sept. 9 season opener at FedEx Field, Kelly’s NFL coaching debut with the Philadelphia Eagles, about being properly prepared on defense, physically and mentally, to deal with the fast-break offensive approach that Kelly was bringing to the pro game.

And then they promptly went out and seemed to have no answers whatsoever at the outset as the Eagles rolled up big offensive numbers in the first half and coasted to a 33-27 triumph over the Redskins on opening night. The rematch comes Sunday in Philadelphia, and the Redskins know they must be far more successful in slowing down the Eagles’ up-tempo offense if they’re going to begin putting their season back together after a 3-6 start.

“I don’t know if other teams are not prepared for it,” Redskins defensive end Kedric Golston said. “I think some would say we weren’t prepared for it the first game. And obviously looking at the result you could say yeah, we weren’t. I beg to differ. I think that there’s a difference between a pace beating you and just somebody not being in their gap or missing tackles. I think it’s two different things.”

Whatever the reasons, the Eagles ran 53 plays and amassed 21 first downs and 322 yards of total offense in the first half of the opener. Redskins cornerback DeAngelo Hall scored a touchdown on a bizarre play on which he picked up the ball after an apparent incomplete pass that instead was ruled a lateral and a fumble, then raced to the opposite end zone basically without being pursued. But that was the lone bright spot early on for the Redskins as the Eagles raced to a 33-7 lead early in the third quarter.

“Obviously that was a first game and we didn’t know what to expect completely,” Redskins safety Reed Doughty said. “We prepared for it completely. We prepared all summer for it. I don’t think the coaches could have done anything else conditioning-wise to prepare you for that. I think that we’ve seen what it is on film. We’ve experienced that with Denver, with some other teams [that run fast-paced offenses] as well. So I don’t think the conditioning aspect should be a big issue.”

The Post Sports Live crew offers bold predictions for what will happen when the Redskins face the Eagles in Philadelphia on Sunday. (Post Sports Live/The Washington Post)

The Eagles managed only 24 offensive plays, five first downs and 121 yards in the second half of the opener. Even so, they finished the game with 263 rushing yards, 184 of them by tailback LeSean McCoy.

“We’ve got to stop the run better this time,” Redskins linebacker Ryan Kerrigan said. “Yeah, [quarterback] Nick Foles has been playing well these past couple games. But we allowed 200-some rushing yards the last game. That’s gonna be our focus, I know, this week. . . . We knew it was gonna be fast. We had prepped for that. Of course it’s always different when you see it in a live game speed. But we weren’t caught off guard by the pace or anything.”

Said Golston: “I think that it was something that obviously was talked a lot about in college and obviously them saying they wanted to get 90 plays in the game. And they did get a lot of plays in. But I think we were really prepared for it. We practiced it every day in training camp. . . . The pace didn’t surprise anybody. It wasn’t a lack of, you know, not lining up or not being able to get the [defensive play] calls or anything like that. It was just they beat us, bottom line.”

The Eagles are first in the league in rushing offense and fourth in total offense. McCoy is the NFL’s leading rusher. Foles has taken over at quarterback for Michael Vick, who played the opener against the Redskins, and has totaled 10 touchdown passes in the past two games, wins at Oakland and Green Bay that evened the Eagles’ record at 5-5 and moved them into a first-place tie in the NFC East with the Dallas Cowboys. Foles has thrown 16 touchdown passes and no interceptions this season.

Hall said the Eagles have been “kind of rolling these last couple weeks,” but the Redskins will be helped “immensely” by the previous meeting.

“I wasn’t fatigued,” Hall said. “Fatigue didn’t play into anything that happened while I was out there. But just a variety of plays and just not to know what to expect was a little overwhelming at times. So that definitely plays a part in a lot of their success against us. . . . We’ll see Sunday. We’ve got a good dose of what they’re gonna do. They know what we’re gonna do. And we’ll get out there and may the best man win.”

Said Doughty: “I think there’s a lot you learn. It’s the first time anybody had seen their offense. I think we’ve got some tape on them. And we know they’re fast paced. We know they like big strikes. Hopefully we can limit those. . . . Obviously they can run the football and LeSean McCoy is very, very dynamic. We’ll see what the game plan is.”

The Redskins’ offense also must do its part after failing to sustain drives in the early going on opening night, putting even more pressure on the defense.

“They got us on our heels early,” Doughty said. “Once you’re down a few scores, it’s hard to come back on offense like that because it opens up everything and it takes away our ability to run the ball. So we’re definitely gonna have to start on a better foot this time.”