The Eagles' season-long Darren Sproles injury mystery deepened Thursday, when the team confirmed a report from ESPN's Adam Schefter that Sproles aggravated his hamstring problem in his return to practice Wednesday, sidelining the running back for Sunday night's visit from the Dallas Cowboys.

Eagles coach Doug Pederson said just before practice Wednesday that he expected Sproles to play against Dallas, for the first time since the season opener. Sproles, 35, injured his hamstring in practice the next week. He was a partial practice participant once in late September and again Wednesday.

Typically, a player who will be out more than three or four weeks is placed on injured reserve, but it seemed throughout September and October that Sproles might be close to returning. The word was that the team was being extra careful that the injury was fully healed.

The Eagles waived returner DeAndre Carter, who was doing a good job in Sproles' absence, on Tuesday, when it seemed Sproles was ready. Carter was picked up off waivers Wednesday by the Houston Texans. It seems likely that newcomer Golden Tate will inherit return duties.

This latest Sproles setback means the Eagles' decision against seeking running-back help at the Oct. 30 trade deadline will be second-guessed. Jay Ajayi suffered a season-ending knee injury on Oct. 7 against the Vikings, leaving the team with Wendell Smallwood, Corey Clement, and rookie Josh Adams.

"I know he wants to be out there," Smallwood said of Sproles, who was not available for comment. "I talk to him almost every day. The fact that he sees us stepping up to the job, and it's kind of not a falloff, he gets excited for what we're doing and how we're doing it. He tells us, 'Continue to keep holding it down, keep doing your job,' not having them look for him to rush back."

The saga of the Eagles' continued faith in the recovery of a 35-year-old back who missed most of last season with arm and knee injuries is likely to be scrutinized further .