Ryan Kerrigan thinks Saturday’s preseason game against the Bills will help prepare the Redskins defense to face the Eagles in the season opener (John McDonnell/Washington Post)

The Washington Redskins will be the first team to face the up-tempo offense of the Philadelphia Eagles’ new coach, Chip Kelly, in a regular season game when the two teams meet in the opener Sept. 9 at FedEx Field. The Redskins defense gets a warm-up of sorts when it faces the offense of the Buffalo Bills in a preseason game Saturday.

The Bills use similarly fast-paced tactics, and the Redskins regard this game as valuable preparation.

“I think it’s going to be really, really helpful,” linebacker Ryan Kerrigan said Wednesday. “We’ve been working some up-tempo in practice and whatnot. But really getting the live-game reps at it is going to be really, really crucial for us. The Bills, especially, they don’t waste any time. They get up to the line of scrimmage and they snap it right away. So it’ll be good for us from a conditioning standpoint and just a mental standpoint to kind of know what to expect Week 1.”

Facing such an offense challenges the conditioning of the players on a defense, and makes it more difficult for a team to make the substitutions that it normally would make.

“That’s the hard part because in some cases you want to get the nickel defense out there,” Kerrigan said. “In some cases you want to have the base defense out there. But it’s tough to make those substitutions when they’re going full throttle and full speed. That’s the challenge that it presents. That’s, I think, one of the main points of running that kind of offense is it causes a lot of, not panic, but it doesn’t allow the defense to get the kind of personnel they want.”

Kerrigan said Redskins players have not yet begun preparing to face the offensive system that Kelly is bringing from the college game at Oregon to the NFL with the Eagles.

“As a unit, we haven’t spent any time on Philly yet,” Kerrigan said. “But I know the coaches have been really breaking down a lot of Oregon film and just looking at here and there checking out some Philly games. We’re not over-preparing right now but just little tidbits here and there.”

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What’s ahead:

● Blog posts on the quarterback shuffle and Redskins’ Park renovations.

● Thursday’s practice is at 1 p.m. Defensive coordinator Jim Haslett speaks afterward.

More on the Redskins and NFL:

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Injured NT Barry Cofield optimistic he’ll be ready for opener

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