PHILADELPHIA (973espn.com) - The Eagles' running back situation was a concern coming into training camp.

That burden may have reached a critical mass on Wednesday when it was revealed that projected starter Ryan Mathews was placed on the non-football injury list with an ankle injury suffered while working out on his own last week.

The designation itself is likely an indication that Mathews can't pass the conditioning test scheduled for Thursday morning before Philadelphia begins its first full-scale team practice in the afternoon.

He can be activated at any time so it's hardly a death knell with six weeks to go before the start of the season but with Mathews' injury history and the team's lack of depth at the position, it's certainly not a positive development.

The 33-year-old Darren Sproles is currently second of the depth chart but his size makes him strictly a sub-package player. Next in line is fifth-round draft choice Wendell Smallwood with Kenjon Barner trying to hold off versatile rookie Byron Marshall for the fourth slot.

Doug Pederson spoke glowingly of Smallwood earlier in the day.

"I was excited when we drafted him," the coach admitted. "I was excited during rookie camp when we had him in here, the entire offseason program, and he came back ready to go in a great frame of mind. He’s going to put himself in a position, I'm hoping, to help us this season. I think he's that good.

"Excellent route runner, good hands, patient runner, and I love the fact that he's kind of a one-cut, no-nonsense type guy. He's a downhill guy but fast enough to separate and create some long runs. So I'm excited, again, once we start getting into pads, protection, how well can he protect? A lot of backs in college that come to this level, that's something that they've got to learn extremely fast."

In other roster news, the Eagles added former Hampton receiver David Watford to the 90-man roster as the replacement for linebacker Travis Long, who was released earlier in the day.

Meanwhile, long-snapper Jon Dorenbos was the only veteran who didn't report but it was an excused absence related to his stint on "America's Got Talent" and he is scheduled to re-join the team on Thursday.

-John McMullen covers the Eagles and the NFL for 973espn.com. You can reach him at jmcmullen44@gmail.com or on Twitter @JFMcMullen