Rookie linebacker Ryan Kerrigan was back on the practice fields on Tuesday morning, an indication that his injured knee was improving.

Kerrigan was limited in work, though, and he wore a brace to protect the knee from further injury.

Kerrigan participated in the team's walk-through portion of practice, but when it came time for 11-on-11 work he stood on the sidelines. He was replaced in the lineup by Rob Jackson.

Asked about Kerrigan's status, head coach Mike Shanahan said he could be limited for another two or three days.

"[Athletic trainers] are going to be a little more cautious than usual," Shanahan said. "We want to make sure he is ready to go. He has never been set back by injuries, so once he had a little setback, we want to make sure he is healthy before we throw him out there."

Kerrigan suffered the injury on the first day of training camp. He said his knee bumped into the knee of another player and it swelled up on him after practice.

"I think it'll heal quickly," he said. "I'm taking it day to day."

Is the injury impacting Kerrigan's ability to learn the Redskins' defense?

"I think a little bit, but I'm still able to take mental reps," Kerrigan said. "It's just physically I'm not able to do it, I'm not able to develop that muscle memory on plays I'm missing out on."

Said Shanahan: "It's not hard to learn the position and he is getting all of the mental reps. He's out there and he's watching film. There's always a big difference in doing than watching it, and he's eager to get out there.

"We're just afraid that if we put him  out there too quick, we're going to set him back. An ounce of prevention can be a pound of cure."