PHILADELPHIA -- Eagles All-Pro left tackle Jason Peters left Thursday's practice with an injury during the first team-period of the session.

Peters dropped to the ground and was slow to get up before walking to the sideline to receive attention from the training staff prior to departing indoors on one of the first snaps of an 11-on-11 drill practicing run plays.

According to multiple reports, Peters suffered a quad strain and is expected to miss some time.

Matt Tobin replaced Peters at left tackle following the injury and Lane Johnson remained at right tackle, perhaps an early indication that the injury is not believed to be severe enough to facilitate Johnson moving to left tackle in Peters' absence, which would likely be the plan should the veteran go down with an injury during the regular season.

Meanwhile, the Eagles defense took a hit when Pro Bowl safety Malcolm Jenkins grabbed his leg after covering Jordan Matthews during an early-session drill and ultimately returning indoors with the training staff as well.

In addition to Peters' injury, the Eagles were once again without running backs Ryan Mathews and Wendell Smallwood along with wide receiver Marcus Johnson and right guard Brandon Brooks.

Wednesday was the first time since Andy Reid's final training camp in 2012 that the Eagles returned to live hitting in full pads during practice.

"It's tackle football," head coach Doug Pederson said Wednesday, when asked to explain why he believes in tackling during camp. "It's a physical game. It's that competition. It's knowing that we're going to put the pads on and go to the ground today. This is the first time outside of cutting our own players, being able to tackle and drive through guys, I think it's so important to be able to do that, to be in the right place and position defensively. It just makes it different. The tempo of that practice intensifies during those live periods."

Matt Lombardo may be reached at MDLombardo@yahoo.com. Follow him on Twitter @MattLombardo975. Find NJ.com Eagles on Facebook.