Andy Reid hardly ever strays from the main practice field at the NovaCare Complex.
So when the Eagles' coach waddled over to an adjoining field Monday to watch one-on-one drills between his offensive and defensive lines, there could be just one reason.
Reid wanted to see if Jamaal Jackson, in his first full practice back as the starting center, and his surgically repaired left knee could withstand live hitting from flesh-and-bone defensive tackles.
After Jackson took on a few bull-rush moves from Antonio Dixon and Mike Patterson - and survived when a lineman fell onto his braced knee - Reid walked away seemingly pleased.
"Today was a huge step for me," said Jackson, who walked off the field with a slight limp. "I was talking about little steps back [at training camp], but today was a big step. So now I can start taking some even bigger steps and try and get back into that old form."
Reid said Monday that he was going to push Jackson, who is less than eight months removed from surgery to correct a torn anterior cruciate ligament, and push him he did. The 30-year-old took every repetition with the first team and, even though he won't play in Thursday's preseason finale, Jackson is on track to start the season opener against Green Bay.
"That's my goal," Jackson said. "But a lot can change from now and Sept. 12."
Jackson's return could bring stability to the interior of an offensive line that has been in flux. The musical chairs continued Monday with Todd Herremans back on the shelf. The left guard, who spent most of training camp rehabbing with Jackson as he rested his sore left foot, sprained his right ankle on Sunday.
Herremans downplayed the injury, but it comes just a week after his return from a long layoff. Mike McGlynn, no longer needed at center - at least for the time being - slid over to fill in at left guard.
At right guard, Stacy Andrews' hold on the spot has become precarious since Reid said a week ago that Andrews "needs to keep getting better." Apparently, he has not. Max Jean-Gilles split repetitions at practice with Andrews by the end of last week. This week, Nick Cole, who recently returned from swelling in his knee, has shared first-team practice time with Andrews.
Andrews, acquired in 2009 as a free agent, missed most of last season as he recovered from ACL surgery and learned a new system. It's no secret that he also has struggled with the move from tackle to guard.
"I've worked on [playing guard] a lot and felt a whole lot better," Andrews said. "Of course, in [Cincinnati] I played right tackle most of my years. I started 25 games there and three at right guard."
And what is the biggest difference between the two positions?
"At tackle, you're more on an island. You're one-on-one with the defensive end," Andrews said. "And at guard, you're helping the center and the tackle."
The Eagles split snaps between Andrews and Jean-Gilles early last season, so a repeat this year isn't out of the question.
"We're shuffling in and out all the time so they get used to doing that," Eagles quarterback Kevin Kolb said. "And then I get used to it and everybody gets used to it. It's not an issue if we go with guys at different positions from Day 1."
If Jackson makes it back by the Packers game, it will be his fifth straight opener as the starter. He said he's "not trying to be a phenomenon" in terms of his quick rehabilitation, and that the Eagles haven't rushed his return because Cole and McGlynn were shaky.
"It's never been one of those things, 'Aw, we need you out here. We need you out here,' " Jackson said. "It's always been, 'How do you feel about doing this? How do you feel about doing that?' "