Looking back, Macho Harris doesn't know whether it was something he ate, or a case of a stomach virus, or just an out-of-this-world illness that knocked him out of practice for most of last week during the Eagles' mini-camp for rookies and selected veterans. All he knows is that, after losing a few pounds and a few practices, he is back where he belongs: On the field and digging in to the Eagles' defense.

Harris is an interesting prospect to watch at this camp. A fifth-round pick who was a standout cornerback at Virginia Tech, Harris is learning the defense first at free safety here. It is not an easy chore, because the free safety is the primary signal caller in this scheme, and he has to be right just about every snap of the football.

Combine that mental strain with the new world of bigger, more mature men who take more experienced angles and how know how to do the little things to get ahead, and you can appreciate the road Harris has to take.

"I love the challenge," he said. "I'm treasuring this opportunity. This is a dream come true, to be in this defense and with this team. Everything about it is great for me. This is a hard defense to learn, no doubt about that. But that is when your discipline takes over, when you know that you have to be a student of the game. I am that kind of player. You just can't be a football player and go out and play safety in this league. You have to be a student of the game.

"I have to know the whole defense. The safety is the brain of the defense and we have to know formation shifts, changes, adjustments we need to make. It's going to take a little bit of time to get my feet wet and settle in, but I know I can play. I can play ball in this league. I know that."

Harris had heard "rumors" that he might get moved to safety in the NFL, and so far that has been where he has played in his five weeks as an Eagle. There is still a chance that the Eagles will give Harris time at cornerback, too, to see if they can develop a young player to help at both positions down the line.

At Virginia Tech, Harris was a "boundary" cornerback who had to man up and play physical, no-fear football to support the run. He was excellent in pass coverage, too, using his aggressiveness and his strength as advantages.

"I'm in the box there, and we played man-to-man coverage probably 80 percent of the time. I'd see a fullback coming out on a linebacker and know that it was me and the running back," said Harris. "A lot of things run through your mind real fast. You have to be confident in your abilities. It was physical. I loved it. I love being aggressive, and that's why this system is so good for me. Here, I have a lot of responsibility. Free safety, man, I watched Brian Dawkins here for so long and I loved him. It would have been great to have had the chance to learn from him, but that isn't the case.

"It's ball. We're playing ball. This is a business and I'm here and I'm loving it."

The Eagles are high on Harris, and for good reason. He is a smart kid, a tenacious player and he has the kind of motor that fits in perfectly to the scheme. How quickly Harris dissects the X's and O's and then goes out and plays at his top speed is likely the key to his short-term development.

In the meantime, Harris is just glad to be back on the field. He was able to sit in on meetings and memorize his playbook last week, even though he was too sick to practice. Given the competition at safety -- with Quintin Mikell, Quintin Demps, Sean Jones and Rashad Baker ahead of him -- Harris has his work cut out. It isn't going to be easy to make this team, much less earn playing time.

Welcome to the big leagues, kid.

"That's fine with me," he said. "I never expected to be given anything and I don't think that will ever be the case. You have to work hard for what you want. I want to make it here. I am going to work as hard as I can to do that, and I know that every day I get a little bit more knowledgeable in the defense.

"I'm in the NFL. Staying here and doing what I want to do isn't going to be easy. I understand that."