Starting left guard Todd Herremans, held out of the Eagles' workouts this week because of a left-foot injury, flew to North Carolina on Thursday to meet with Robert Anderson, a foot and ankle specialist who has worked with other NFL players.

Herremans missed the first five games last season with a stress fracture in the foot before returning for the rest of the campaign. He wrote on his Twitter account that it was "just a checkup," although a flight to an out-of-state doctor indicates something more involved.

"The doctor thinks he'll be all right," coach Andy Reid said.

"All is well," Herremans tweeted later in the day.

Herremans' absence, however, has put a second offensive-line starter on the sideline. Center Jamaal Jackson, described by Winston Justice as the line's leader, almost certainly will miss training camp and possibly the start of the season as he tries to come back from a torn anterior cruciate ligament in his left knee.

The two are part of a growing list of Eagles dealing with tears, tweaks, and ruptures, putting a spotlight this week on the team's backups, many of whom are either inexperienced or the same veterans who struggled in relief roles last year.

Safety Marlin Jackson was likely lost for the season Tuesday when he ruptured his Achilles tendon, thrusting highly touted but untested second-round draft pick Nate Allen into a potential starter's role.

Others returning from serious 2009 injuries have been taking their comebacks slowly. Cornerback Ellis Hobbs, who had a herniated disk in his neck last year, sat out Thursday's session.

Middle linebacker Stewart Bradley, back after suffering a torn anterior cruciate ligament in August, left practice early Wednesday and did not participate Thursday, although he said he only had a calf cramp.

Running back LeSean McCoy also was out of practice Thursday with what the team called a "tweaked" ankle.

The Eagles have downplayed most of the injuries, noting that there are three months until the start of the regular season. At this stage, coaches likely are being cautious with even minor problems.

The most significant cause for concern appears to be on the offensive line. With two starters already hurt, the team also has to watch right guard Stacy Andrews, who had a fitful 2009 as he returned from a torn knee ligament.

Nick Cole is working with the first team at center. Max Jean-Gilles, who recently had lap-band weight-loss surgery, has stepped in for Herremans.

Jean-Gilles said the linemen working with the first team are experienced, especially after having to play in a 2009 season in which the unit was shuffled by injuries.

"Everybody who's in there has already played, so we're not missing a heartbeat at all," Jean-Gilles said. "It's not the first time it's ever happened."

Aside from Marlin Jackson's injury, Reid said he is "not real concerned" with the other maladies his players have faced so far.

Bradley, for one, was pushing a wheelbarrow of wet cement as he helped build a playground at an Eagles charity event on Thursday. He wore a sleeve over his left calf and had a wrap or pad underneath, but said he had "just cramped up," likely from dehydration.

Before Wednesday, Bradley had moved well in practice. But if he faces any in-season setbacks as he returns from his knee injury, the team will have to turn to the same cast that tried to replace him last year: Joe Mays and Omar Gaither, who is coming off a foot injury that limited him to five games in 2009.

Behind Hobbs, rookie Trevard Lindley is the only major cornerback addition.

Reid said he was "fine" with his team's depth.

"We've got plenty of people in those spots that could play," he said. "We're fine."