Eagles guard Evan Mathis will be out for an extended period after an MRI revealed an MCL sprain of his right knee on Monday, an NFL source said.

The sprain isn't Grade 1 and likely Grade 3, which could take anywhere from 4-8 weeks to return from. The Eagles may opt to place Mathis on Injured Reserve-designated to return, which would keep him off the roster for eight weeks. Mathis will get a second opinion on Wednesday.

Allen Barbre, who has been filling in for the suspended Lane Johnson at right tackle, has a high ankle sprain and could be out for several weeks, a source said. Barbre will see a foot specialist this week.

Eagles coach Chip Kelly said Monday afternoon that he had yet to met with the team's trainers and didn't have an update on the injuries. He also would not speculate about his options on the line if Mathis and/or Barbre are out.

With Mathis and Barbre out for an extended period, the Eagles will likely look to Andrew Gardner and Dennis Kelly. Top backup Matt Tobin is recovering from a high ankle sprain. The Eagles may also be forced to sign an offensive lineman off the street or call up either Kevin Graf or Josh Andrews from the practice squad to supplement their losses.

If Gardner and Kelly are the replacements, the Eagles offensive line for Monday's game against the Colts will likely look like: left tackle Jason Peters, left guard Dennis Kelly, center Jason Kelce, right guard Todd Herremans and right tackle Andrew Gardner.