ARLINGTON, Texas -- Eagles safety Reed Blankenship limped off the field during the third quarter against the Dallas Cowboys and has not returned to the game yet. He has been ruled questionable to return with a thigh injury.

Sydney Brown has replaced Blankenship and could finish out Sunday's game playing next to rookie Drew Mukuba. The Eagles gave up a touchdown on the drive Blankenship got hurt. Now, they only lead 21-14 over the Cowboys with 13:09 remaining in the fourth quarter.

Blankenship remains on the sideline with his teammates, trying to get back into the game. The Eagles' secondary could struggle without Blankenship's steady presence. Brown lost the starting free safety job to Mukuba during training camp and has made little impact during his first three NFL seasons.

Eagles cornerback Adoree' Jackson was also placed in concussion protocol and is questionable to return. New acquisition Michael Carter II has moved into the slot and second-year cornerback Cooper DeJean has replaced Jackson on the boundary.