Rookie outside linebacker Ryan Kerrigan went through his first practice since July 29 without a hitch and said he hopes to play in Friday’s preseason opener against Pittsburgh.

Kerrigan hyperextended and bruised his right knee on the first day of training camp practices and had been sidelined ever since. In the last three practices, he gradually ramped up his activity level – working in positional drills and walk-throughs. On Monday, Kerrigan practiced without limitation at the starting left outside linebacker spot.

“I wasn’t thinking about it at all,” said Kerrigan, who wore a brace on the knee. “Felt great to be out there to practice with my teammates after a week off, and now I’m happy to be out there with them again.”

Said Redskins coach Mike Shanahan: “Good to see him back, and I’m sure he’s not 100 percent, but it’s good to see him in the swing of things.”

Shanahan said he hasn’t determined whether Kerrigan will play Friday, but Kerrigan believes he can, and has to play.

“I’ve got to be ready. I have no choice,” said Kerrigan, who is converting from defensive end to linebacker and counts every snap as vital. “The game’s in four days. I have to keep working and practicing to get myself as prepared as possible.”

Kerrigan said he already feels knowledgeable of the Redskins’ schemes and his assignments. But he knows physical comfort will come with more repetitions.

“I didn’t [feel lost]. I’ve been taking a lot of mental reps and spending a lot more time with [linebackers] coach Lou Spanos than I normally would have,” Kerrigan said. “So it was good to do that, so today when I got out there, I knew what was going on. …

“It’s just a whole different animal from defensive end. You talk about coming out of a two-point stance versus a three-point stance. I’m still working on that and doing my stance right so I can do that and come off the line of scrimmage while being explosive, and of course the coverage factor, because that’s one of the biggest elements of playing linebacker opposed to defensive end.”