BETHLEHEM, Pa. - DeSean Jackson contorted his lithe body, made the catch, and dropped to the ground like a bag of footballs.

A fan yelled, "Get up, I just bought your hat!"

But Jackson wasn't getting up.

The Eagles' star wide receiver lay on the grass, writhing in pain.

In that moment and in the moments soon after - the rush of trainers to the scene, Jackson getting up wobbly and almost falling again, the cart ride to the locker room with his head buried in his arm - there was a collective deep breath.

Or was it the skipping of a heartbeat?

"Yeah, especially for a quarterback," Kevin Kolb said.

Jackson injured his back and was still being evaluated, the Eagles said after practice. But about a half hour later, Jackson walked out of the locker room on his own, eased himself into his black Porsche, and sped away without comment.

His teammates and Eagles sources said the injury was minor, and the fact that Jackson walked away from the locker room suggested as much. One team source said that the pain was concentrated toward Jackson's lower back and that it was too soon to say when he could return.

Nevertheless, the scare put into perspective the old adage that "you're only a play away." It might have even more meaning for someone who stands 5-foot-10 and weighs 175 pounds, as Jackson does.

His injury highlighted an eventful day of training camp, when the full squad practiced in full pads for the first time and in front of a full house.

On a picture-perfect day, an announced training camp crowd of 8,238 was treated to the highs - and lows - that come from a young team. There were spectacular throws and dropped passes, sound collisions and missed blocks, signs of unity and plenty of fights.

But the Jackson jolt stood out for obvious reasons. With a new quarterback under center, the third-year Pro Bowl receiver is expected to be of extra importance.

"Yeah, you definitely need him out there," Kolb said.

The injury happened in the afternoon no-pads session during a seven-on-seven drill. Kolb threw to Jackson on a slant, but the ball was slightly behind the receiver, and he twisted to pull it in. Cornerback Asante Samuel was covering and linebacker Omar Gaither was converging, but there was no contact.

"I told Coach, 'I didn't touch him. I don't know what happened,' " Gaither said.

Jackson went down, got on all fours, then fell over. After a few seconds, the training staff came running out. Coach Andy Reid even walked over to survey the damage. When Jackson finally, s-l-o-w-l-y got up, he almost collapsed again. But head trainer Rick Burkholder and another trainer had a hold on him and helped him to the sideline.

Jackson appeared to be favoring his right leg as he limped along. He sat down as a cart made its way over and picked him up. Jackson stepped gingerly into the front seat, and the 23-year-old, visibly distraught, leaned his head on his forearm.

Perhaps, for a brief moment, Jackson was thinking about the new contract he wants so dearly. Because of the new 30 percent rule in the collective-bargaining agreement that restricts pay increases for players still working under their rookie contracts, a new deal is unlikely this year.

Jackson has avoided reporters since his arrival at training camp Thursday. Reid said he wants to just focus on football. That could be a problem if this injury keeps him on the sidelines for an extended period.

"He's a tough dude," safety Quintin Mikell said. "I expect him to get back as soon as possible."