Philadelphia Eagles head coach Chip Kelly has revealed that safety Earl Wolff sustained a knee injury in his side's win over the Chicago Bears.

Wolff made his return to action against Marc Trestman's side after four games out with the problem but just a quarter into the match he re-aggravated the ailment, and is now facing a fight to be fit to face the Dallas Cowboys on Sunday.

"We were ahead, and then obviously he's been out for a while, so we were just going to try work him back in the lineup," Kelly told the Philadelphia Inquirer.

"And then we got a lead and we didn't feel like we needed to put him back out there. We'll see how he goes this week."

Philadelphia can secure their place in the post-season with a win over the Cowboys on Sunday.