Still recovering from surgery to repair a torn anterior cruciate ligament, Marlin Jackson spent much of practice Thursday resting on one knee as the Eagles' defense went through team drills.

Organized team activities for Eagles rookies and selected veterans began last week and continue Monday through Thursday at the NovaCare Complex.

Jackson said that coaches ordered him to rest as a precaution and that he was happy to participate in any way just six months after his surgery. But the sight of Jackson on the sideline was a reminder of the uncertainty at free safety heading into the Eagles' second year without Brian Dawkins.

The team has a mix of young and veteran options, but each carries question marks heading into training camp.

There is Jackson, who, because of twin ACL tears, has played just 11 games over the last two seasons with the Colts. Second-round draft pick Nate Allen has a shot at the job, but he is obviously untested. Macho Harris is another option, though he played cornerback at minicamp last week. Also available is Quintin Demps, but he had a shot to lock up the position last year and didn't.

For his part, Jackson, who tore his left ACL in October and his right one in 2008, brushed off concerns about his readiness and sounded eager to jump into a defense he called "aggressive."

"You didn't see me go today. That wasn't by my choice," he said. "I wanted to go today, but I also know I have to be smart, you know?"

He said he was "blessed" to be able to participate in workouts so soon after surgery. "When you get any hint of tendinitis, you have to pull back a little bit and give yourself a day or two to rest," he said.

Jackson dismissed reports that he was moving with a limp Wednesday in what was his first practice since getting hurt.

"I know if you ask any coach who watched me practice, they'll tell you I look fine," Jackson said. He said he felt good and explosive so far and described returning to practice as the next step in his rehabilitation.

Jackson, who spent his first five seasons with the Colts, has played both cornerback and safety. The Eagles signed him to an incentive-laden contract in March, and Jackson said he was expected to play free safety. Jackson said Dawkins was his favorite player, citing the former Eagle's passion.

He was enthusiastic when discussing his transition to a new defensive scheme.

"We're going to dictate to you. We're going to dictate the tempo of the game, and that's what I like about this. It's an aggressive defense," Jackson said.

Jackson, from Sharon, Pa., near Pittsburgh, grew up as a Steelers fan. In Sharon and Indianapolis, he began a youth education program called Fight for Life that he hopes to bring to Camden this year.

The organization provides after-school programs that encourage positive behavior in schools and communities. Students who participate can advance along a board made up like a football field to win prizes. Jackson also plans to give out school supplies, he said.

He expects a launch party in August.

Contact staff writer Jonathan Tamari at 215-854-5214 or jtamari@phillynews.com.