The MRI on Byron Maxwell revealed a sternoclavicular joint sprain, where the collarbone connects to the sternum, a source close to the situation told the Daily News on Monday.
The source said Maxwell might be unlikely to play Saturday, when the 6-8 Eagles try to keep their playoff hopes alive against the 7-7 Washington Redskins and an array of passing-game weapons that includes former Eagle DeSean Jackson.
There still are several NFC East playoff scenarios, but for the Eagles, all of them involve defeating Washington.
Maxwell and the other starting corner, rookie Eric Rowe, left Sunday night's loss to Arizona in the first half, Rowe with a concussion, There was no word on Rowe's status.
The source said key Eagles special-teams performer (and wide receiver) Seyi Ajirotutu also is doubtful for this week with an ankle sprain suffered against the Cardinals, who lost their most dynamic defensive player, safety Tyrann Mathieu, for the season to an ACL tear. Matheiu suffered that while returning a late Sam Bradford interception.